A-44 | November 2013
SCHRIFTENREIHE SCHIFFBAU
Philipp Russell
The Sinking Sequence of
M.V. Costa Concordia
Institute of
Ship Design and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
Master’s Thesis
The Sinking Sequence of
M.V. Costa Concordia
Philipp Russell
Registration Number 20837662
First Examiner:
Prof. Dr.-Ing. Stefan Krüger
Second Examiner:
Prof. Dr.-Ing. Moustafa Abdel-Maksoud
Hamburg, November 3, 2013
Declaration of Authorship
I hereby declare and confirm that this thesis and the work presented in it have
been generated by me as the result of my own original research and that I have
not made use of any other sources than those stated in here.
(Place, Date)
(Philipp Russell)
Contents
Contents
List of Figures
III
List of Tables
VI
Nomenclature
VII
1 Introduction
1
2 Theory
2.1 Flow Calculation . . . . . .
2.1.1 Small Openings . . .
2.1.2 Large Openings . . .
2.2 Flooding Process . . . . . .
2.2.1 Flux Integration . . .
2.2.2 Pressure Propagation
2.3 Grounding Model . . . . . .
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2
2
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3
5
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3 Accident
9
3.1 Description of the Ship . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 Summary of the Accident . . . . . . . . . . . . . . . . . . . . . . . 9
3.3 Timeline of Events . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4 Model
4.1 Hydrostatic Model .
4.2 Loading Condition .
4.3 Compartment Model
4.4 Opening Model . . .
4.5 Watertight Doors . .
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5 Results
5.1 Reference Case . . . . . . . . .
5.1.1 Flooding Progression . .
5.1.2 Influence of the Different
5.1.3 Final Equilibrium . . . .
5.2 Study of Influences . . . . . . .
5.2.1 Rock Moment . . . . . .
5.2.2 Wind Moment . . . . . .
5.2.3 Stabiliser Moment . . .
5.2.4 Watertight Door 6 . . .
5.2.5 Watertight Door 9 . . .
5.2.6 Watertight Door 10 . . .
Institute of Ship Design
and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
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Compartments
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I
Contents
5.3
5.4
5.5
5.2.7 Watertight Door 24 . . . . . . . . . . . . . .
Most Likely Scenario . . . . . . . . . . . . . . . . .
5.3.1 Overview . . . . . . . . . . . . . . . . . . .
5.3.2 Influence of the Damaged Compartments . .
5.3.3 Heel Change to Starboard . . . . . . . . . .
5.3.4 Influence of the Undamaged Compartments
5.3.5 Progressive Flooding of Deck 0 . . . . . . .
5.3.6 Second Grounding . . . . . . . . . . . . . .
Grounding Effects . . . . . . . . . . . . . . . . . . .
Hypothetical Scenarios . . . . . . . . . . . . . . . .
5.5.1 Sinking at Sea . . . . . . . . . . . . . . . . .
5.5.2 No Leak in Watertight Door 24 . . . . . . .
5.5.3 All Watertight Doors Closed . . . . . . . . .
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6 Conclusion
82
References
86
Institute of Ship Design
and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
www.ssi.tu-harburg.de
II
List of Figures
List of Figures
2.1
2.2
2.3
2.4
2.5
2.6
3.1
3.2
3.3
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
Flow through small openings . . . . . . . . . . . . . . . . . . . . . .
Flow through large openings . . . . . . . . . . . . . . . . . . . . . .
Integration stripe for large openings . . . . . . . . . . . . . . . . . .
Flooding graph of M.V. Costa Concordia’s initial damage . . .
Simplified subdivision model and openings of M.V. Costa Concordia’s initial damage, sections of Deck A and on the Centreline .
Predictor-corrector scheme for ω = 0.5 . . . . . . . . . . . . . . . .
M.V. Costa Concordia . . . . . . . . . . . . . . . . . . . . . . .
Course of M.V. Costa Concordia . . . . . . . . . . . . . . . . .
M.V. Costa Concordia in her final position . . . . . . . . . . .
Hydrostatic model of M.V. Costa Concordia . . . . . . . . . .
Righting lever curve of M.V. Costa Concordia before the accident
Bulkhead plan of M.V. Costa Concordia . . . . . . . . . . . . .
Upper deck plan of sister ship . . . . . . . . . . . . . . . . . . . . .
Lower deck plan of sister ship . . . . . . . . . . . . . . . . . . . . .
Real leak and opening model, port side . . . . . . . . . . . . . . . .
Opening model of M.V. Costa Concordia . . . . . . . . . . . .
Watertight doors on Deck C, aft . . . . . . . . . . . . . . . . . . . .
Watertight doors on Deck C, midship . . . . . . . . . . . . . . . . .
Watertight doors on Deck C, forward . . . . . . . . . . . . . . . . .
Watertight doors on Deck B, forward . . . . . . . . . . . . . . . . .
Watertight doors on Deck A, aft . . . . . . . . . . . . . . . . . . . .
Watertight doors on Deck A, midship . . . . . . . . . . . . . . . . .
Watertight doors on Deck A, forward . . . . . . . . . . . . . . . . .
Floating position development in the reference case . . . . . . . . .
Damage zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Volume fluxes into the compartments above the double bottom in
the reference case . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Volume fluxes into the compartments in the double bottom in the
reference case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Escape trunk on Deck C in Compartment 4 . . . . . . . . . . . . .
Deck A in Compartment 4 . . . . . . . . . . . . . . . . . . . . . . .
Water volumes in the rooms in Compartment 4 in the reference case
Heeling moments of the rooms in Compartment 4 in the reference
case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Water volumes in the rooms in Compartment 5 in the reference case
Heeling moments of the rooms in Compartment 5 in the reference
case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Water volumes in the rooms in Compartment 6 in the reference case
Institute of Ship Design
and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
www.ssi.tu-harburg.de
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III
List of Figures
5.12 Heeling moments of the rooms in Compartment 6 in the reference
case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.13 Water volumes in the rooms in Compartment 7 in the reference case
5.14 Heeling moments of the rooms in Compartment 7 in the reference
case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.15 Water volumes in the rooms in Compartment 8 in the reference case
5.16 Heeling moments of the rooms in Compartment 8 in the reference
case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.17 Righting lever curve at the equilibrium in the reference case . . . .
5.18 Fire door at frame 44 in the reference case viewed from aft . . . . .
5.19 Rock stuck in the leak . . . . . . . . . . . . . . . . . . . . . . . . .
5.20 Floating position development with rock moment . . . . . . . . . .
5.21 Lateral area of M.V. Costa Concordia . . . . . . . . . . . . . .
5.22 Floating position development with wind from starboard . . . . . .
5.23 Floating position development with wind from port . . . . . . . . .
5.24 AIS track of M.V. Costa Concordia . . . . . . . . . . . . . . .
5.25 Ship speed and stabiliser moment according to AIS track . . . . . .
5.26 Floating position development with stabiliser . . . . . . . . . . . . .
5.27 Position of portside stabiliser after the accident . . . . . . . . . . .
5.28 Watertight Door 6 . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.29 Volume flux through Watertight Door 6 . . . . . . . . . . . . . . . .
5.30 Water volumes in Compartments 7 and 8 with activation of WTD 6
5.31 Heeling moments of Compartments 7 and 8 with activation of WTD 6
5.32 Floating position development with activation of WTD 6 . . . . . .
5.33 Watertight Door 9 . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.34 Volume flux through Watertight Door 9 . . . . . . . . . . . . . . . .
5.35 Water volumes in Compartments 4 and 5 with activation of WTD 9
5.36 Heeling moments of Compartments 4 and 5 with activation of WTD 9
5.37 Floating position development with activation of WTD 9 . . . . . .
5.38 Watertight Door 10 . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.39 Volume flux through Watertight Door 10 . . . . . . . . . . . . . . .
5.40 Water volumes in Compartments 3 and 4 with activation of WTD 10
5.41 Heeling moments of Compartments 3 and 4 with activation of WTD
10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.42 Floating position development with activation of WTD 10 . . . . .
5.43 Watertight Door 24 . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.44 Volume flux through Watertight Door 24 . . . . . . . . . . . . . . .
5.45 Water volumes in Compartments 3 and 4 with activation of WTD 24
5.46 Heeling moments of Compartments 3 and 4 with activation of WTD
24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.47 Floating position development with activation of WTD 24 . . . . .
5.48 Leaking types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Institute of Ship Design
and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
www.ssi.tu-harburg.de
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IV
List of Figures
5.49
5.50
5.51
5.52
5.53
5.54
5.55
5.56
5.57
5.58
5.59
5.60
5.61
5.62
5.63
5.64
5.65
5.66
5.67
5.68
5.69
5.70
5.71
5.72
5.73
5.74
5.75
5.76
5.77
5.78
5.79
5.80
5.81
5.82
5.83
5.84
5.85
5.86
5.87
5.88
M.V. Costa Concordia at 21:48 UTC . . . . . . . . . . . . . . .
Floating position at 21:48 UTC in the most likely scenario . . . . .
Floating position development in the most likely scenario . . . . . .
Main switchboard rooms at the time of the blackout . . . . . . . . .
Water volumes in Compartment 6 in the most likely scenario . . . .
Heeling moments of Compartment 6 in the most likely scenario . . .
Water volumes in Compartment 7 in the most likely scenario . . . .
Heeling moments of Compartment 7 in the most likely scenario . . .
Water volumes in Compartment 5 in the most likely scenario . . . .
Heeling moments of Compartment 5 in the most likely scenario . . .
Volume flux through Watertight Door 24 in the most likely scenario
Water volumes in Compartment 4 in the most likely scenario . . . .
Heeling moments of Compartment 4 in the most likely scenario . . .
Water volumes in Compartment 8 in the most likely scenario . . . .
Heeling moments of Compartment 8 in the most likely scenario . . .
Deck A in Compartment 3 . . . . . . . . . . . . . . . . . . . . . . .
Garbage plant on Deck 0 . . . . . . . . . . . . . . . . . . . . . . . .
Water volumes in Compartment 3 in the most likely scenario . . . .
Heeling moments of Compartment 3 in the most likely scenario . . .
Water volumes in Compartment 2 in the most likely scenario . . . .
Heeling moments of Compartment 2 in the most likely scenario . . .
Rooms on the freeboard deck (Deck 0) . . . . . . . . . . . . . . . .
Volume fluxes due to progressive flooding . . . . . . . . . . . . . . .
Water volumes on deck 0 in the most likely scenario, part 1 . . . . .
Heeling moments of deck 0 in the most likely scenario, part 1 . . . .
Water volumes on deck 0 in the most likely scenario, part 2 . . . . .
Heeling moments of deck 0 in the most likely scenario, part 2 . . . .
Water volumes on deck 0 in the most likely scenario, part 3 . . . . .
Heeling moments of deck 0 in the most likely scenario, part 3 . . . .
M.V. Costa Concordia at 21:55 UTC . . . . . . . . . . . . . . .
Floating position at 21:55 UTC in the most likely scenario . . . . .
Floating position development while grounding . . . . . . . . . . . .
Final floating position with a seabed stiffness of 50 t/m . . . . . . .
Final floating position with a seabed stiffness of 5 t/m . . . . . . .
Floating position development while sinking at sea . . . . . . . . . .
Critical openings while sinking at sea . . . . . . . . . . . . . . . . .
Immersion of Deck 4 while sinking at sea . . . . . . . . . . . . . . .
Floating position development without leak in Watertight Door 24 .
Floating position development with all watertight doors closed . . .
Floating position at 21:55 UTC with all watertight doors closed . .
Institute of Ship Design
and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
www.ssi.tu-harburg.de
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V
List of Tables
List of Tables
3.1
3.2
3.3
4.1
4.2
4.3
4.4
4.5
4.6
5.1
5.2
5.3
Main particulars of M.V. Costa Concordia . . . . . . . . .
Important events . . . . . . . . . . . . . . . . . . . . . . . . .
Flooded compartments . . . . . . . . . . . . . . . . . . . . . .
Comparison of the cross-curves of stability . . . . . . . . . . .
Loading condition of M.V. Costa Concordia before sinking
Opening types and collapsing pressure heights . . . . . . . . .
Watertight door activity outside the damaged compartments .
Watertight door activity inside the damaged compartments . .
Failure of watertight doors . . . . . . . . . . . . . . . . . . . .
Data used for the wind heeling moment . . . . . . . . . . . . .
Water exchanged through watertight doors . . . . . . . . . . .
Leaking values of different openings . . . . . . . . . . . . . . .
Institute of Ship Design
and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
www.ssi.tu-harburg.de
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VI
Nomenclature
Nomenclature
AIS
BSU
Automatic Identification System
Bundesstelle für Seeunfalluntersuchung (Federal Bureau
of Maritime Casualty Investigation)
DB
Double Bottom
EU
European Union
FLOODSTAND Integrated Flooding Control and Standard for Stability
and Crises Management
MCIB
Marine Casualties Investigative Body
MFZ
Main Fire Zone
MODU
Mobile Offshore Drilling Unit
SOLAS
International Convention for the Safety of Life at Sea
UPS
Uninterruptible Power Supply
UTC
Coordinated Universal Time
VDR
Voyage Data Recorder
WTD
Watertight Door
Latin Letters
dV
dz
dz
x
R
x
A
B
C
Cd
CL
D
F
g
H
LOA
LP P
M
p
p
Volume difference
Pressure height difference
Earth-fixed clearance to seabed
Earth-fixed coordinate
Rotation matrix
Ship-fixed coordinate
Cross section area
Moulded breath
Seabed stiffness
Discharge coefficient
Lift coefficient
Depth
Force
Gravitational constant
Water depth
Length over all
Length between perpendiculars
Moment
Air pressure
Position vector
Institute of Ship Design
and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
www.ssi.tu-harburg.de
[m3 ]
[m]
[m]
[m]
[−]
[m]
[m2 ]
[m]
[N/m]
[−]
[−]
[m]
[N ]
[m/s2 ]
[m]
[m]
[m]
[N m]
[P a]
[m]
VII
Nomenclature
Q
R
s
T
t
TCB
u
V
v
V CB
VS
w
z
Volume flux
Righting lever of stabiliser
Integration variable lying in the opening plane
Draught
Time
Transverse Centre of Buoyancy
Water velocity
Volume
Ship speed
Vertical Centre of Buoyancy
Service speed
Cross-curve of stability
Water level
[m3 /s]
[m]
[m]
[m]
[s]
[m]
[m/s]
[m3 ]
[kn]
[m]
[kn]
[m]
[m]
Pressure difference independent of water level
Relaxation factor
Heeling angle
Dissipative energy term
Density of water
Trim angle
[m]
[−]
[◦ ]
[m2 /s2 ]
[kg/m3 ]
[◦ ]
Greek Letters
α
ω
ϕ
ψ
ρ
ϑ
Subscripts
c
p
Corrector-related terms
Predictor-related terms
Institute of Ship Design
and Ship Safety
Prof. Dr.-Ing. Stefan Krüger
www.ssi.tu-harburg.de
VIII
1
INTRODUCTION
1 Introduction
The M.V. Costa Concordia sank in the early morning of January 14, 2012 near
the island of Giglio in the Mediterranean Sea. The night before she had hit an
underwater rock when performing a tight high-speed turn very close to the shore.
As a result of this collision she drifted powerless near to the harbour of Giglio.
Here she grounded a second time and evacuation procedures were started. The
list gradually increased until she finally capsized and came to rest on the rocks in
shallow waters.
Thirty-two the 4229 persons on board lost their lives during the flooding and
capsizing of the ship. Because twelve of the victims were Germans, the Federal
Bureau of Maritime Casualty Investigation (BSU) is obligated to conduct an investigation in addition to the official one performed by the Italian Marine Casualties
Investigative Body (MCIB) [10]. In the scope of this investigation the BSU cooperates with the Institute of Ship Design and Ship Safety at the Hamburg University
of Technology.
The accident will be simulated by means of a progressive flooding simulation.
Using this simulation the sequence of events is to be reproduced in order to gain
insight into the possible failure modes. The influence of opening and closing watertight doors is of particular interest and will be determined in detail. In addition,
the role of the second ground contact near the harbour as well as the influence of
wind and other possible external moments shall be investigated.
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THEORY
2 Theory
The sinking simulation program used to investigate the accident has been developed at the Institute of Ship Design and Ship Safety at the Hamburg University
of Technology [3]. It utilises a quasi-static approach, which is able to determine
the flooding of a ship and the resulting floating position in the time domain. The
ship is subdivided into compartments with corresponding openings. The volume
fluxes through these openings are calculated using the incompressible, rotationaland viscous-free Bernoulli equation. At each time step the new filling level of each
compartment is computed so that the resulting floating position can be determined
by hydrostatic means. Air compression as well as conditions for the openings like
time-dependent activations or collapsing pressure heights can be taken into account. The following is a short abstract of the underlying physical model used for
the simulation, further details can be found in [3].
2.1 Flow Calculation
According to the Bernoulli theorem the energy along a streamline is constant and
consisting of pressure, kinetic and potential parts. This holds for an irrotational
and stationary flow of an incompressible and inviscid fluid and can be formulated
as follows:
Z
u2
ψ
1
dp +
+ z − = const.
(2.1)
2g
g
p ρg
The first three terms in equation 2.1 describe the mentioned energy parts, whereas
the term ψ allows for pressure losses to be modelled.
2.1.1 Small Openings
In the case of small openings, i.e. no change in cross section and velocity across
the opening, there are two relevant modes of flow. These are the free outflow as
shown in figure 2.1 on the left side and the deeply submerged flow pictured on
the right of the same figure. Neglecting the dissipative term for now the pressure
height difference becomes
pa − pb u2a − u2b
ψab
+
+ za − zb −
= dz ,
ρg
2g
g
(2.2)
wherein some terms can be neglected depending on the type of flow. The velocity
at the opening is in each case given by
p
u = 2g · dz .
(2.3)
The pressure losses are now considered by a discharge coefficient Cd
p
u = Cd · 2g · dz
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THEORY
reducing the flow velocity. This coefficient is semi-empirical and accounts for the
contraction of the flow as well as viscous effects. It visually depicts the ratio of the
flow cross section behind the opening in relation to the opening area. For a normal
opening it assumes a value of around 0.6. The resulting volume flux through the
opening is then given by
dV
= Q = A · u.
(2.5)
dt
pa
za
pb
pa
a
pb
a
za
b
z0
b
zb
z0
zb
Figure 2.1: Flow through small openings [3]
2.1.2 Large Openings
In the case of large openings the flow velocity and the cross section area can differ
over the opening extension, leading to a more complex flux calculation. However,
the two basic modes free outflow and deeply submerged flow can superpose any
possible flow situation, as shown in figure 2.2. For the deeply submerged part
equation 2.2 can be used to determine the flow velocity.
(1)
(2)
za
h2
za
h1
zb
(4)
(3)
zb
za
h2
h2
h1
h1
(5)
zb
(6)
za
za
h2
h1
za
zb
h2
h1
h2
zb
h1
zb
Figure 2.2: Flow through large openings [3]
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The volume flux of the free outflow part on the other hand demands an approach
considering the position and form of the large opening. For this purpose the
opening, which is in general a polygon stretching in any direction, is divided by
stripes in z-direction. This way the velocity can be described in the earth-fixed
z-direction, while the integration to obtain the volume flux is performed in sdirection, as shown in figure 2.3.
h2
za
z1
y1
z0
s1 y(s)
s
s
y
h1
z1
y0
z
z0
z
y
Figure 2.3: Integration stripe for large openings [3]
The shape function of the z-stripe is a linear variation of the form
y(s) = y0 + s ·
y1 − y0
,
s1
(2.6)
while the free outflow velocity can be determined through
p
p
u(s) = 2g · za − (z0 + sz · s) + α
pa
pb
u2
with α =
−
+ a
ρg ρg 2g
z1 − z0
and sz =
.
s1
(2.7)
The term α contains the pressure differences independent of z, while sz contains
information about the orientation of the opening [3]. To get the volume flux of the
free outflow part, the integration
Z
Z Z
Z s1
Q=
u dA =
u(s) dy ds =
u(s) · y(s) ds
(2.8)
A
s
y
0
needs to be performed. Solving the integral for equation 2.6 and 2.7 yields the
analytical solution for the volume flux through one stripe:
3
3
5
5
2 p
2(y1 − y0 )
2
2
2
2
· 2g · y1 · h1 − y0 · h0 +
· (h1 − h0 )
Q=−
3sz
5(z1 − z0 )
(2.9)
with h1 = h(s1 ) = za − z1 + α and h0 = h(0) = za − z0 + α
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THEORY
2.2 Flooding Process
The flooding paths of the ship are modelled using graph theory with the compartments as nodes and directed edges representing the various openings. An
identification number is assigned to all compartments ascending from keel to top,
from bow to stern and from port to starboard. The direction of the edges joining
the compartments is then defined positive if connecting ascending identification
numbers. This direction is only a sign convention and does not have to represent
the actual flooding direction.
An example of a flooding graph is shown in figure 2.4 for a simplified case of
the initial damage of M.V. Costa Concordia. In the actual model there are
several cases of multiple openings between compartments, especially to represent
the damage, but these have been omitted here for simplification purposes. The
arrangement of the compartments and openings involved in this sample flooding
graph is demonstrated in figure 2.5. As is evident from these pictures, representing
the actual model with nodes and edges allows for a quicker identification of vital
openings and neighbourhood relationships.
(3) WB.DB.11C
(4) WB.DB.12C
2
(2) WB.DB.10C
3
1
(1) Outside
5
6
(8) Fwd D/G Stairs
9
(5) VO.DB.6C
4
(9) Aft D/G PS
10
(12) Refrigeration
Compressors
8
15
(6) Fwd D/G PS
(13) Switchboard PS
13
17
(7) Fwd D/G SB
(14) Switchboard SB
7
12
11
(11) Electric
Motors
14
(10) Aft D/G SB
16
Figure 2.4: Flooding graph of M.V. Costa Concordia’s initial damage
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THEORY
Swbd. SB 16
17
.
.
8
Refr. Compr.
Electric Motors
12
Compartment
VO.DB.6C
4
Aft D/G SB
Fwd D/G SB
.7
z
x
Deck A
. 14 . 13
.4
.3
5
WB.DB.12C
WB.DB.11C 2
6
7
. .1
7
6
WB.DB.10C
8
5
Fwd
D/G
Strs.
15
9
Aft D/G PS
Swbd. PS
Fwd D/G PS
11
10
14
13
17
y
x
Electric Motors
Centreline
Swbd. SB
Aft D/G SB
Fwd D/G SB
16
Figure 2.5: Simplified subdivision model and openings of M.V. Costa Concordia’s initial damage, sections of Deck A and on the Centreline
2.2.1 Flux Integration
The overall flux to or from a certain compartment is formed by the sum of all
the fluxes through each opening to this compartment. By integrating the flux
over a set time interval the water volume transferred between the compartments
is obtained:
Z t
2
dV (t) =
Qo (t) dt
(2.10)
t1
Using this volume, the new water levels inside the compartments can be calculated.
This calculation has to be done in an iterative way due to the arbitrary geometric
structure of the compartments and thus non-linear relationship between volume
filling and water level. Furthermore, the flux Qo (t) also depends non-linear on
the water level. To consider these non-linearities in the calculation, a weighted
predictor-corrector scheme is employed to determine the exchange of water volume
between the compartments:
dVc = dt · (ω · Qo (tp ) + (1 − ω) · Q∗o (t0 )) ,
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THEORY
dVc = ω · dVp + (1 − ω) · dV0 .
(2.12)
flux Q(t)
In there ω denotes the relaxation factor, which is set to 0.5. A relaxation factor
stabilises an iteration for a given value below 1, as is the case here. The predictorcorrector scheme is then applied as visualised in figure 2.6.
dV0 (2.)
dVc (5.)
dVp (4.)
Qo (t0 )
Q∗o (t1 )
dt
t0
t1
time t
Figure 2.6: Predictor-corrector scheme for ω = 0.5 [3]
2.2.2 Pressure Propagation
In the case of several neighbouring compartments being totally flooded there is
a non-linear coupling between these compartments because the calculation of the
fluxes cannot be independently performed. Therefore some requirements need to
be met:
- The sum of all fluxes to and from a compartment has to be zero.
- Water flowing from partially full compartments must spread through the full
compartment.
- The free variable to be determined is the pressure in the full compartment.
The resulting non-linear equation system is constructed using a sub-graph of the
related filled compartments. If for instance the compartment containing the portside aft diesel generators is completely full of water, the governing equation yields:
p
Q = A6 · ρg · (z1 − z9 ) + p1 − p9
p
+ A10 · ρg · (z6 − z9 ) + p6 − p9
p
(2.13)
+ A11 · ρg · (z9 − z11 ) + p9 − p11
p
+ A14 · ρg · (z9 − z10 ) + p9 − p10
p
+ A15 · ρg · (z9 − z13 ) + p9 − p13 = f (p9 ) = 0 .
This non-linear equation can be solved with respect to the unknown pressure p9
employing an iterative algorithm to answer the pressure propagation problem.
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2.3 Grounding Model
In the scope of a semi-submersible heavy lift ship accident the presented sinking
simulation program has been enhanced to consider reaction forces due to grounding
[4]. This will be important in the later phase of the M.V. Costa Concordia
event.
The position and movement of a ship can be described in two basic coordinate
systems, a ship-fixed one with axes specified by Latin letters and an earth-fixed
one with Greek letter axes. Both have their origin in the aft perpendicular on
the centreline, but the ship-fixed one is located at the keel and moves with the
ship, while the earth-fixed lies on the water surface and does not move. Either
coordinate system is right-handed with x or ξ positive in forward direction, y or η
positive to port and z or ζ positive upwards. For hydrostatic purposes only three
degrees of freedom are relevant, namely the draught T , the trim angle ϑ (positive
if the bow is deeper submerged than the stern) and the heeling angle ϕ (positive
to starboard). Therefore the relation between the two coordinate systems can be
described using a rotation matrix R:
x=R·x−t
 
    
ξ
cos ϑ sin ϕ sin ϑ cos ϕ sin ϑ
x
0
η= 0




cos ϕ
− sin ϕ
· y − 0
ζ
− sin ϑ sin ϕ cos ϑ cos ϕ cos ϑ
z
T
(2.14)

(2.15)
Forces and moments are added up within the earth-fixed system and the hydrostatic equilibrium is then found in an iterative way. To consider the influence of
ground contact, the seabed is represented by springs. At each time step every
point of the hydrostatic model with the position vector p is checked for contact
with the seabed, positioned in a certain depth H. Using the third row vector r3 of
the rotation matrix R,
(2.16)
dz = H − r3 · p + T
yields the earth-fixed distance dz between point and seabed. If this value is greater
than zero, the seabed with the stiffness C exerts a grounding force of
F = C · dz ,
(2.17)
otherwise there is no force due to ground contact. This force additionally leads to
trim moments Mη and heeling moments Mξ , which can be determined using the
first and second row vector of the matrix R:
Mη = F · ξ = F · r1 · x
(2.18)
Mξ = F · η = F · r2 · x
(2.19)
The forces and moments resulting from ground contact are then added to the
existing ones, so that they affect the equilibrium.
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ACCIDENT
3 Accident
3.1 Description of the Ship
The M.V. Costa Concordia was built in 2004 by Fincantieri in Sestri Ponente
for the Italian cruise line Costa Crociere. Her main particulars are given in table
3.1 and a picture of the vessel in undamaged condition is shown in figure 3.1.
Table 3.1: Main particulars of M.V. Costa Concordia [10]
Length over all
Length between perpendiculars
Breadth
Depth
Summer draught
Service speed
LOA
LP P
B
D
T
VS
290.20
247.70
35.50
11.20
8.30
19.60
m
m
m
m
m
kn
Figure 3.1: M.V. Costa Concordia (Source: Costa Crociere)
3.2 Summary of the Accident
Having left the port of Civitavecchia near Rome on the evening of January 13,
2012 the ship was on her way to Savona in Northern Italy with 3206 passengers
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ACCIDENT
and 1023 crew on board. En route she changed her planned course and headed
for Giglio at a speed of over 15 knots where she was to perform a tight starboard
turn near the coast. In doing so she collided with the “Scole Rocks” below the
waterline on her port side, so that five watertight compartments were hit. These
contained amongst others the electric propulsion motors, all diesel generators as
well as the main switchboard. The initial list was to port due to the leak being on
that side and because of the heeling moment caused by the contact with the rocks,
which stuck inside the vessel after the impact. After a while the flooding became
almost symmetrical and the ship went upright again. Having been damaged in
compartments vital for power generation, power distribution and propulsion, she
was soon adrift without electricity. Even though the emergency diesel generator
started up, it did not work reliable enough to provide power. Thus, emergency
power was supplied by UPS batteries. However, the steering gear did not function
and thrusters needed more than emergency power. So, due to wind and current the
vessel was eventually moved north of Giglio harbour. There the forces of nature
turned her around 180 degrees and pushed her in the direction of the island until
she grounded a second time, as shown in figure 3.2.
Figure 3.2: Course of M.V. Costa Concordia [10]
At this time the evacuation procedures were started, while the heeling angle to
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ACCIDENT
starboard continuously increased. In the early hours of the next morning, she had
finally capsized and sunk onto the seabed approximately 25 metres deep. There
she had been laying in a position pictured in figure 3.3 until she was at last raised
on September 16, 2013.
Figure 3.3: M.V. Costa Concordia in her final position (Source: Getty Images)
3.3 Timeline of Events
To check the results of the sinking simulation against the real situation, a timeline
of important events needs to be established. In this case, “important” refers to
incidents relevant to the sinking process, which means ascertained progress of flood
water, actions inducing heeling moments and the development of the heeling angle.
Therefore, occurrences concerning passenger safety and evacuation are omitted
here, although they are of course relevant for the investigation of the BSU. An
interesting sociological study on the events during the accident has been performed
at the Bielefeld University, which led to the release of vital VDR data by the
Italian consumer protection organisation Codacons [2]. Times stated in this thesis
are UTC, the local time at Giglio is UTC plus one hour. The running time in
seconds serves to verify the relevant events during the sinking simulation, which is
started at the time of the impact. Heeling angles are given positive to starboard
and hence negative to port. The decks of M.V. Costa Concordia below the
freeboard deck, which is named Deck 0, are labelled C to A in ascending order
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ACCIDENT
starting above the double bottom. The source of the information compiled in
table 3.2 is the official investigation report from the Italian Marine Casualties
Investigative Body and VDR data available to the Institute of Ship Design and
Ship Safety through the BSU and the MCIB [10] [13] [14]. In addition, the BSU
has ordered a photogrammetric expertise from the Leibniz University Hannover
on the floating position at the time of dropping the starboard anchor, 21:48 UTC
[16].
Table 3.2: Important events [10] [13] [14] [16]
UTC
[hh:mm:ss]
t [s]
Heel [◦ ]
20:45:07
20:46:55
20:52:25
22:00:57
21:10:00
21:26:30
0
108
438
950
1493
2483
<0
-10 to -15
<0
<0
>0
<10
Collision
Blackout occurred
Water reported on Deck A
Compartments 5, 6 and 7 confirmed flooded
Ship begins to drift towards shore
Water reported on Deck 0
21:48:00
3773
14 - 14.5
Starboard anchor dropped, -1.2◦ trim
21:55:00
22:11:26
23:34:00
4193
15
5179 25 to 30
10133
90
Event
Second grounding / Lifeboats begin to launch
25 to 30 degrees starboard heel reached
Capsize
As shown in here, immediately after the accident the ship heels to port due to the
impact by the rocks below the centre of gravity and due to the starboard turn.
Shortly thereafter, the blackout happens, indicating the contact of flood water
with vital electrical components. In some parts of the Italian investigation there is
an earlier time stated for the blackout, namely at 20:45:58 after 51 seconds. The
final blackout however shows clearly after 108 seconds according to the monitoring
of the watertight doors on the VDR [14]. Water in the Main Switchboard Room
on Deck A is reported seven minutes after the collision, and another eight minutes
later three of the five damaged compartments are indicated to be flooded. These
are Compartments 5, 6 and 7 with their contents as per table 3.3. Compartment
4 is also heavily flooded, while Compartment 8 only suffered a minor leak in the
double bottom. During the flooding of these compartments the ship lists about
10 to 15 degrees to port, as can be seen in several passengers’ videos. This is
supported by the wind, which blows from north-north-east at approximately 10
knots onto the starboard side of the vessel.
Some 25 minutes into the accident, the list of the ship changes from port to
starboard due to the flooding becoming more symmetrical. This coincides with
the turning of the vessel and her drifting towards the island, which means that
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ACCIDENT
the wind is now coming from the port side. Approximately 40 minutes past the
collision water reaches the freeboard deck, Deck 0, while it heels the ship almost
10 degrees to starboard.
The starboard anchor is dropped one hour and a few minutes after the accident
after several failed attempts. According to the photogrammetric evaluation the
ship has a starboard list of about 14 to 14.5 degrees at that time. This order of
magnitude of the heeling angle is supported by the statement of a bridge officer
around the same time. The trim angle is determined to be 1.2 degrees, which
results in a trim of 5.19 metres to the aft. There is of course some measuring
inaccuracy so that the real angles may differ slightly. Nevertheless these values
are the most reliable ones because they are not based on observations made by the
crew in a stressful situation. Thus, they will serve as a reference point.
One hour and ten minutes subsequent to the first grounding the vessel grounds
a second time with the aft starboard side. At the same time the first lifeboats are
launched, starting on the starboard side to reduce the list. The last heeling angle
stated by the crew on the VDR is 25 to 30 degrees to starboard at 22:11:26 UTC.
Almost three hours after taking the damage the vessel capsizes assuming a heeling
angle of around 90 degrees as confirmed by a coastguard helicopter. From here on
she sinks completely and comes to rest on the rocks with a list of approximately
70 degrees.
Table 3.3: Flooded compartments [10]
Compartment
Contents
Deck
4
Refrigeration compressors
Crew cabins
C
A
5
Void space
Electric propulsion motors
Synchroconverters
Double Bottom
C
A
6
Water ballast tank
Aft diesel generators
Incinerators
Main switchboard
Double Bottom
C
C
A
7
Water ballast tank
Forward diesel generators
Lube oil purifiers
Engine workshop
Double Bottom
C
C
A
8
Water ballast tank
Double Bottom
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MODEL
4 Model
4.1 Hydrostatic Model
Figure 4.1: Hydrostatic model of M.V. Costa Concordia
The hull form of the vessel is modelled up to and including Deck 11 and the funnel
using plans of M.V. Costa Concordia and an identical sister ship [12] [8]. This
results in the hydrostatic model shown in figure 4.1. The cross-curves of stability
w (ϕ) = TCB · cos (ϕ) + V CB · sin (ϕ)
(4.1)
of this model are then checked against the ones of the loading computer, as presented in table 4.1.
Table 4.1: Comparison of the cross-curves of stability [12]
Cross-curve
Model [m] Loading computer [m] Relative deviation [%]
w (10◦ )
w (20◦ )
w (30◦ )
w (40◦ )
w (50◦ )
w (60◦ )
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3.299
6.584
9.583
11.835
13.243
14.363
3.295
6.556
9.552
11.786
13.095
14.325
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0.1
0.4
0.3
0.4
1.0
0.3
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MODEL
Differences in the given order of magnitude are to be expected because it is not
possible to reproduce the exact lines of the vessel using the given plans. Given
this limitation, the quality of the model is considered to be acceptable for the
intended purpose. In contrast to classical hydrostatics, where only the water- or
weathertight part is used, the sinking simulation requires the whole hull including
the superstructure.
4.2 Loading Condition
Table 4.2: Loading condition of M.V. Costa Concordia before sinking [12]
Shell plating factor
Density of sea water
1.002 1.025 t/m3
Ships weight
Longitudinal centre of gravity
Transverse centre of gravity
Vertical centre of gravity (solid)
Free surface correction of V.C.G.
Vertical centre of gravity (corrected)
Draught at A.P (moulded)
Draught at LBP/2 (moulded)
Draught at F.P (moulded)
Trim (pos. fwd)
Heel (pos. stbd)
Volume (incl. shell plating)
Longitudinal centre of buoyancy
Transverse centre of buoyancy
Vertical centre of buoyancy
Area of waterline
Longitudinal centre of waterline
Transverse centre of waterline
Metacentric height
54998.680
118.610
-0.010
16.850
0.344
17.194
7.901
8.115
8.328
0.427
0.320
53657.242
118.632
-0.081
4.388
7988.557
111.632
-0.072
1.711
t
m.b.AP
m.f.CL
m.a.BL
m
m.a.BL
m
m
m
m
Deg.
m3
m.b.AP
m.f.CL
m.a.BL
m2
m.b.AP
m.f.CL
m
The loading condition of M.V. Costa Concordia at her departure from Civitavecchia is given in table 4.2. It is pretty close to the design state with a slight
forward trim and almost no heel. The associated righting lever curve is depicted
in figure 4.2. All of the relevant intact stability criteria are fulfilled, including the
weather criterion, passenger heeling and turning circle moment. The righting lever
curve itself with the high initial metacentric height is typical for a cruise ship to
comply with comfort requirements.
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MODEL
LC PRIOR DAMAGE
starboard side
2
Righting lever [m]
1.5
1
0.5
0
-0.5
-1
0
10
20
30
40
Heeling angle [deg]
GZ [m]
Requ. or Max. h: 0.971 m
Progfl. or Max.: 56.945 Deg.
50
60
70
GM at Equilib. : 1.711 m
Area under GZ [mrad]
Figure 4.2: Righting lever curve of M.V. Costa Concordia before the accident
4.3 Compartment Model
Using the bulkhead plan of M.V. Costa Concordia in figure 4.3 and the deck
plan of an identical sister ship in figures 4.4 and 4.5, the compartmentation of the
ship is modelled. This is done in the confinements of the hydrostatic model, which
means up to and including Deck 11, because this is the last continuous deck. All
rooms are assumed to be fully ventilated, so that air compression is neglected.
The fire-proof A-class walls and decks are expected to prevent the spread of water,
thus they form the main compartment boundaries. Furthermore, certain B-class
barriers like cabin walls also determine compartments, but are modelled with large
openings as described further down. Lifts, staircases and large spaces are modelled
as one compartment with the appropriate vertical extension. The permeability
of the compartments is set to SOLAS standards, that is 0.6 for stores, 0.85 for
machinery spaces and 0.95 for every other space [5]. Though certain simplifications
concerning the compartment model need to be made, the whole ship still consists
of 642 compartments.
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Figure 4.3: Bulkhead plan of M.V. Costa Concordia [12]
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Figure 4.4: Upper deck plan of sister ship [8]
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Figure 4.5: Lower deck plan of sister ship [8]
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4.4 Opening Model
Compartments are connected to each other and to the sea via one or more openings.
The state of the openings is derived from the given plans; a door normally closed
is modelled as closed and vice versa. Each of these openings needs a name, the
identification numbers of the compartments to connect, coordinates of the opening
centre and spatial extensions in the relevant directions. Furthermore, values for
the semi-empirical discharge coefficient and the collapsing pressure heights are
required. The allowable heights of water pressing on an closed opening before it
collapses depend on the type of the opening and are given in table 4.3. These
values are in line with classification society requirements and results of the EU
project FLOODSTAND [15].
Table 4.3: Opening types and collapsing pressure heights [15] [12]
Opening type
Collapsing pressure height [m]
Non-weathertight opening
Elevator door
Fire door
Cold store door
Weathertight opening
Splashtight door
Window
Watertight door
0.5
1.0
2.0
3.5
5.0
8.0
20.0
50.0
As described above, the discharge coefficient for most of the openings is set to 0.6.
However, there are some exceptions to this rule. The first one applies to groups of
small similar openings like cabin windows, which are treated as one large opening
to reduce the modelling effort. The volume flux Q through the simplified opening
shall be the same as through the n original ones with their individual discharge
coefficient Cd,0 = 0.6 [3]:
Q = Cd,new · Alarge · u = n · Cd,0 · Asmall · u
(4.2)
Therefore, it holds
Cd,new = n · Cd,0 ·
Asmall
Alarge
(4.3)
for the modified discharge coefficient, which is always lesser than 0.6 because the
large opening also contains the areas between the small openings.
In the case of modelling the aforementioned cabin walls, an almost similar approach is chosen, with the cabin walls as large and the cabin doors as small openings. In addition, a probability factor of p = 0.5 is introduced because it is unknown
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which cabin doors are actually open:
Cd,new = p · n · Cd,0 ·
Asmall
Alarge
(4.4)
The last exception in terms of discharge coefficients is the leak itself. It is modelled
with eleven openings using the dimensions given in the official investigation report
as illustrated in figure 4.6. For most of these openings the discharge coefficient
is assumed to be 0.6, only in the case of the rearmost leak it is altered to 0.2 to
account for the obstruction caused by the rock.
4
5
6
7
8
Deck 0
Swbd. PS
Refr. Compr.
Electric Motors
Aft D/G PS
Deck A
Fwd
Fwd D/G PS
D/G
Strs.
Deck B
Deck C
z
x
VO.DB.6C
WB.DB.12C
WB.DB.11C
WB.DB.10C
Figure 4.6: Real leak and opening model, port side [10]
Even with the mentioned simplifications, there are in total 1580 openings defined
to connect the compartments, which are presented in figure 4.7.
Figure 4.7: Opening model of M.V. Costa Concordia
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4.5 Watertight Doors
According to the SOLAS rules in force at the date of keel laying, the subdivision factor, which is dependent on ship type and length, specifies that the M.V.
Costa Concordia has to withstand the flooding of two contiguous watertight
compartments. Therefore, the ship is subdivided into 19 compartments by watertight bulkheads reaching from the keel of the ship to the freeboard deck Deck
0. To allow the crew to pass bulkheads in the watertight part without the detour
via the freeboard deck, the M.V. Costa Concordia is fitted with 25 watertight
doors. These are positioned on the three decks Deck C, Deck B and Deck A at the
various bulkheads, as shown in figures 4.8 to 4.14 with the damage zone marked
in blue.
7
8
10
11
9
Figure 4.8: Watertight doors on Deck C, aft [12]
4
6
3
2
5
1
Figure 4.9: Watertight doors on Deck C, midship [12]
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MODEL
1
Figure 4.10: Watertight doors on Deck C, forward [12]
12
13
Figure 4.11: Watertight doors on Deck B, forward [12]
25
24
Figure 4.12: Watertight doors on Deck A, aft [12]
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23
21
22
19
20
18
Figure 4.13: Watertight doors on Deck A, midship [12]
19
18
17
16
15
14
Figure 4.14: Watertight doors on Deck A, forward [12]
Watertight doors are normally only open during harbour activities. They can
be opened at sea to perform works near them but shall be closed immediately
and their activation shall be noted in the log. With the approval of the flag state
administration some watertight doors may be kept open at sea if deemed necessary.
In the case of M.V. Costa Concordia these exceptions are Watertight Doors
7, 8, 12, 13 and 24.
Any activation of a watertight door is also registered in the VDR. For the minutes
after the accident these activation times from the VDR are given in tables 4.4 and
4.5 regarding the watertight doors outside and inside the damage zone, respectively.
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Table 4.4: Watertight door activity outside the damaged compartments [14]
UTC [hh:mm:ss]
t [s]
WTD 5
WTD 11
WTD 12
WTD 13
20:45:07
20:45:29
20:45:43
20:45:52
20:46:27
20:46:29
20:47:11
20:47:15
20:47:51
20:48:01
20:48:02
0
22
36
45
80
82
124
128
164
174
175
closed
opening
closing
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
opening
closing
closed
open
open
open
open
open
open
closing
closed
closed
closed
closed
open
open
open
open
closing
closed
closed
closed
closed
closed
closed
Table 4.5: Watertight door activity inside the damaged compartments [14]
UTC [hh:mm:ss]
t [s]
WTD 6
WTD 9
WTD 10
WTD 24
20:45:07
20:45:18
20:45:29
20:45:39
20:45:48
20:45:50
20:46:03
20:46:08
20:46:13
20:46:27
20:49:52
20:50:12
20:50:15
0
11
22
32
41
43
56
61
66
80
285
305
308
closed
closed
closed
closed
closed
opening
closing
closed
closed
closed
closed
closed
closed
closed
opening
closing
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
opening
opening
open
open
closing
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
closed
opening
closing
closed
The only doors open at the time of the accident are 12 and 13, which are located
far from the leak near the laundry on Deck B. These two doors are closed almost
immediately by order of the master. Other doors in the damage zone facilitate the
escape of some crew members and are thus opened and closed after the collision
with the rocks. Watertight doors should not be used as an escape route because
every watertight compartment is fitted with vertical escape trunks for this purpose.
In the case of M.V. Costa Concordia however the latter may not have been in
reach due to the entering water.
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MODEL
It has to be noted that the status “open” or “closed” is only updated with some
delay, while the activation times“opening”and“closing”are exact times. Therefore,
in the sinking simulation the opening/closing time of the watertight doors is set
to the minimum of 20 seconds as required by SOLAS and started at these exact
times [5]. If a door is closed again before it is fully opened, the maximum level of
openness is derived from the ratio of passed time to opening time. It also has to
be said that some of the door activations take place after the blackout. However,
the Italian investigators are sure that the operation of the doors is independent
of the main electrical supply, therefore the watertight door activity is modelled as
described above [11].
After some time into the events, the status of several watertight doors changes
to “fault”, shown in table 4.6. This is most likely due to water reaching the sensors
on or near the door. To what extent the mechanical damage of the door is related
to the electrical failure of the sensors remains unknown. Only in the case of
Watertight Door 24 a leak has been reported by witnesses but without details
regarding time or leak size [10].
Table 4.6: Failure of watertight doors [14]
UTC [hh:mm:ss]
t [s]
Heel [◦ ]
Event
22:01:10
22:32:20
22:32:26
22:33:16
22:35:29
963
2833
2839
2889
3022
<0
>10
>10
>10
>10
Failure
Failure
Failure
Failure
Failure
of
of
of
of
of
Watertight
Watertight
Watertight
Watertight
Watertight
Door 24
Door 9
Door 8
Doors 7 and 25
Doors 10 and 11
Furthermore, there are some splashtight doors on the freeboard deck, whose status
is also monitored on the VDR, but these are not opened or closed during the
accident. They are thus modelled according to their opening status and with an
appropriate collapsing pressure height as stated in table 4.3.
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5 Results
Using the presented sinking simulation and the computation model, there are several cases to be calculated. Each of the different influence factors will be considered
independently at first and compared to a reference case. These influence factors
include different induced heeling moments, the activation of watertight doors as
well as leaking through various key openings. In the end a most likely scenario
with the combined influence factors will be presented. Based on this most likely
scenario several hypothetical scenarios will be discussed. Finally, the necessary
conclusions will be drawn.
5.1 Reference Case
5.1.1 Flooding Progression
The first case to be evaluated will serve to demonstrate the initial phase of the
flooding and as a reference case. For this purpose the model as described is used
according to the given plans [12] [8]. In these plans every door has a designated
opening status, which is used for the model. Neither the time-dependent activation
of watertight doors nor external effects are considered. Furthermore, any closed
opening does not leak until the collapsing pressure height is reached.
The calculation of this reference case yields the evolution of the floating position
shown in figure 5.1 starting at the time of the collision.
Draught [m], Trim [m], Heel [deg]
15
Draught
Trim
Heeling angle
10
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.1: Floating position development in the reference case
The water entering through the rupture caused by the rocks immediately heels the
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ship around 14 degrees to port and increases the draught by over 2 metres. Over the
next eight minutes the flooding becomes symmetrical and the heeling changes to
starboard. Twenty minutes into the accident, after the flooding of the last possible
compartments, the vessel reaches an equilibrium at about 12 metres draught at the
aft perpendicular, an aft trim of nearly five metres and approximately 0.5 degree
heeling angle to starboard.
Fwd D/G Strs
Sewage Room
Void 7 pt
Refr. Comp.Ele. Mot.
Deck C
Aft D/G pt
Fwd D/G pt
Aft D/G sb
Fwd D/G sb
Aft Aux.
Void 7 sb
Incinerators
Compartment
4
5
Void 6
6
LO Purifiers
7
8
Wat. Ball. 12 Wat. Ball. 11 Wat. Ball. 10
Double Bottom
Figure 5.2: Damage zone [12]
After the collision with the rocks water enters into five compartments. This is
illustrated in figure 5.2, where the damaged compartments are indicated in red,
while the leaks are shown in blue. Compartments 5 and 6 containing the aft diesel
engines and the electric motors fill up very fast due to the large and unobstructed
leaks. As is illustrated in figure 5.3, the volume fluxes reach 10000 and more cubic
metres per minute. In contrast, Compartment 4 with the refrigeration compressors
as well as Compartments 7 and 8 including the forward diesel engines take more
time to flood. In the case of Compartment 4 this is because of the rock blocking
the still large leak, so that the volume fluxes into the compartment reach only 2000
cubic metres per minute. The leaks in Compartments 7 and 8 are relatively small
and thus take only a few hundred cubic metres per minute on board, but over a
longer time.
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12000
Volume flux [m3/min]
10000
8000
Forward Diesel Engines Stairs
Aft Diesel Engines port 1
Aft Diesel Engines port 2
Electric Motors 1
Electric Motors 2
Refrigeration Compressors
6000
4000
2000
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.3: Volume fluxes into the compartments above the double bottom in the
reference case
The double bottom compartments show the same behaviour as the ones above the
double bottom, as is to be seen in figure 5.4. Void Space 6 and Water Ballast Tank
12 in Compartments 5 and 6 suffer from larger leaks and become flooded within a
minute. Water Ballast Tanks 10 and 11 in compartments 8 and 7 are only affected
by a minor scratch in the hull, so that it takes more time to fill them up.
2500
Volume flux [m3/min]
2000
Water Ballast DB 10C
Water Ballast DB 11C
Water Ballast DB 12C
Void Space DB 6C 1
Void Space DB 6C 2
1500
1000
500
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.4: Volume fluxes into the compartments in the double bottom in the reference case
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As the rooms directly affected by the leak become flooded, the door to the escape
trunk in the Refrigeration Compressors Room marked in figure 5.5 breaks after
the collapsing pressure height of two metres has been reached.
Void 7 pt
Aft D/G pt
Refrigeration Compressors
Electric Motors
Aft Aux. Room
Aft D/G sb
Void 7 sb
Incinerators
Figure 5.5: Escape trunk on Deck C in Compartment 4 [12]
Via the upper exit of this escape trunk marked red in figure 5.6 the water is enabled
to enter the crew spaces on Deck A and spread across the cabins. Apart from the
cabins there are some openings of compartments critical for the upflooding process
also located in this area. These are the doors of the two aft Service Lifts marked
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in yellow in the same figure as well as two doors leading to the staircase of main
fire zones 1 and 2 marked blue in there.
Workshops pt
Buffet Preparation
Deck A Crew 11
Workshops ct
Aft Staircase
Workshops sb
Deck A Crew 12
Figure 5.6: Deck A in Compartment 4 [12]
5.1.2 Influence of the Different Compartments
The amount of flood water in the various rooms of Compartment 4 in this reference
case is indicated in figure 5.7 and the resulting heeling moment in figure 5.8,
wherein positive heeling moments mean a heel to port.
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3000
2500
Volume [m3]
2000
1500
Refrigeration Compressors
Deck A Crew 11.1
Deck A Crew 11.2
Deck A Crew 11.3
Deck A Crew 11.4
Deck A Crew 11.5
Deck A Crew 11 Corridor
Staircase MFZ 1+2
Sum
1000
500
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.7: Water volumes in the rooms in Compartment 4 in the reference case
8000
7000
Heeling moment [tm]
6000
5000
4000
3000
Refrigeration Compressors
Deck A Crew 11.1
Deck A Crew 11.2
Deck A Crew 11.3
Deck A Crew 11.4
Deck A Crew 11.5
Deck A Crew 11 Corridor
Staircase MFZ 1+2
Sum
2000
1000
0
-1000
-2000
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.8: Heeling moments of the rooms in Compartment 4 in the reference case
The most decisive room due to its size is the Refrigeration Compressors Room,
which is flooded first and which determines the heeling moment of this compartment in the first minutes after the accident. As soon as the water reaches Deck A,
the outmost crew cabins (11.1) become relevant for the heel, but the entire water
volume in the crew spaces only adds up to around half of that in the Refrigeration
Compressors Room.
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The situation in Compartment 5 shown in figures 5.9 and 5.10 is different because
it mainly consists of the Electric Motors Room, which dominates the effect of this
compartment. Furthermore, this room also fills up very quick due to the large
leak not being obstructed by a rock. The other rooms in this compartment are
either symmetrical and full in the end or cancel each other out in terms of heeling
moment.
3500
3000
Volume [m3]
2500
Void Space DB 6C
Electric Motors
Synchroconverter Room port
Synchroconverter Room starboard
Sum
2000
1500
1000
500
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.9: Water volumes in the rooms in Compartment 5 in the reference case
12000
Heeling moment [tm]
10000
8000
Void Space DB 6C
Electric Motors
Synchroconverter Room port
Synchroconverter Room starboard
Sum
6000
4000
2000
0
-2000
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.10: Heeling moments of the rooms in Compartment 5 in the reference case
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Compartment 6 is the biggest one of the damaged compartments and has thus
the greatest influence, as is to be seen in figures 5.11 and 5.12. It is transversely
subdivided into the two engine rooms and the Incinerators Room, which flood one
after another from port to starboard. The blackout of the ship about two minutes
after the collision coincides well with the flooding of the second Main Switchboard
Room on the starboard side of Deck A.
6000
5000
Volume [m3]
4000
Water Ballast DB 12C
Aft Diesel Engines port
Aft Diesel Engines starboard
Incinerators Room
Main Switchboard Room port
Main Switchboard Room starboard
Sum
3000
2000
1000
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.11: Water volumes in the rooms in Compartment 6 in the reference case
25000
Heeling moment [tm]
20000
15000
10000
Water Ballast DB 12C
Aft Diesel Engines port
Aft Diesel Engines starboard
Incinerators Room
Main Switchboard Room port
Main Switchboard Room starboard
Sum
5000
0
-5000
-10000
-15000
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.12: Heeling moments of the rooms in Compartment 6 in the reference case
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It takes much more time for the water to enter Compartment 7 because it is
only affected by a small leak in the Engine Staircase and a mere scratch in the
double bottom, which is illustrated in figures 5.13 and 5.14. The time to flood is
amplified by the fact that the Engine Staircase is only a small compartment, which
is only connected via small openings to the portside Forward Engine Room. As
a consequence the qualitative development of the heeling moment differs from the
other compartments with no visible peak.
4500
4000
3500
Volume [m3]
3000
Water Ballast DB 11C
Forward Diesel Engines port
Forward Diesel Engines Stairs
Forward Diesel Engines starboard
Lube Oil Purifiers Room
Engine Workshop
Sum
2500
2000
1500
1000
500
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.13: Water volumes in the rooms in Compartment 7 in the reference case
15000
Heeling moment [tm]
10000
5000
Water Ballast DB 11C
Forward Diesel Engines port
Forward Diesel Engines Stairs
Forward Diesel Engines starboard
Lube Oil Purifiers Room
Engine Workshop
Sum
0
-5000
-10000
-15000
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.14: Heeling moments of the rooms in Compartment 7 in the reference case
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The flooding of Compartment 8, which is only damaged in the double bottom,
points out the significance of intermediate stages of flooding. In the beginning
there is only little water with an extensive lever arm and in the end there is lots of
water with almost no lever arm. The most critical situation however is given as per
figures 5.15 and 5.16 by about 50 per cent filling. Especially in the case of more
complex room geometries, a time domain flooding simulation provides valuable
insight into these intermediate stages in contrast to a pure hydrostatic analysis.
600
Water Ballast DB 10C
500
Volume [m3]
400
300
200
100
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.15: Water volumes in the rooms in Compartment 8 in the reference case
3500
Water Ballast DB 10C
Heeling moment [tm]
3000
2500
2000
1500
1000
500
0
-500
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.16: Heeling moments of the rooms in Compartment 8 in the reference case
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5.1.3 Final Equilibrium
The righting lever curve of the vessel in the equilibrium reached in the reference
case is given in figure 5.17. Due to the special hydrostatic model used by the
sinking simulation, which also incorporates the non-weathertight part of the ship,
the righting levers are positive even for very high angles of heel. Furthermore, the
water volumes in the compartments remain fixed for the calculation of the righting
levers, although in reality they would change with increasing heeling angle.
3
GZ
GM
Righting Lever [m]
2
1
0
-1
-2
-3
-60
-40
-20
0
20
Heeling Angle [deg]
40
60
Figure 5.17: Righting lever curve at the equilibrium in the reference case
There is water pressing on several non-watertight openings on the freeboard deck,
but these are assumed not to leak in the reference case. Therefore, they prevent
progressive flooding via the freeboard deck. The most critical of these openings
due to its size and location is the double fire door on Deck 0 at frame 44, which is
oriented to the stern of the ship and leads into the aft corridor as marked in figure
5.18. The influence of leaking through these openings is investigated further down.
Figure 5.18: Fire door at frame 44 in the reference case viewed from aft
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5.2 Study of Influences
5.2.1 Rock Moment
Figure 5.19: Rock stuck in the leak [12]
During the collision one rock was ripped of the cliffs and stuck in the ship like
pictured in figure 5.19. The rock has an assumed weight of 97 tonnes and an
assumed density of 2.7 t/m3 , which results in a submerged weight of around 60
tonnes. With an estimated transverse centre of gravity of 10.7 metres measured
from the centre line, the rock applies a heeling moment of about 650 tm. This
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is equivalent to a shift of the transverse centre of gravity of the vessel by 11.8
millimetres to port.
To investigate the influence of the rock moment, another calculation is performed
with identical settings as in the reference case, but with the centre of gravity of the
vessel shifted by the named value. The results are given and checked against the
reference case in figure 5.20. The development of draught and trim is practically
the same but the heeling angle evolution differs due to the rock being on the port
side. Initially the influence of the rock moment is small compared to the thousands
of metre tonnes heeling moment applied by the flood water. But as soon as the
crew spaces in Compartment 4 on Deck A begin to flood after about four minutes,
the rock moment is decisive and forces the final equilibrium on the port side.
Draught [m], Trim [m], Heel [deg]
15
Draught reference
Trim reference
Heeling angle reference
Draught with rock
Trim with rock
Heeling angle with rock
10
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.20: Floating position development with rock moment
5.2.2 Wind Moment
To consider the influence of heeling moments due to wind, the lateral area of the
ship shown in figure 5.21 has been entered into the computation model.
The wind velocity and density of air result in a certain pressure, which affects
the lateral area to yield a lateral force. It is assumed that this force is acting on the
centroid of the lateral area above the waterline. The wind force is then equalised
by a hydrodynamic force applied at the centroid of the lateral area below the
waterline so that these two forces form a heeling moment. The heeling moment
also depends on a form-specific drag coefficient as well as on the heeling angle
because lateral area and force application point are reduced with increasing angle.
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Figure 5.21: Lateral area of M.V. Costa Concordia [12]
Table 5.1: Data used for the wind heeling moment [9]
Drag coefficient
Density of air
Draught
Lateral area above waterline
Lateral area centroid above baseline
Wind velocity
Wind direction
1.200
1.225
8.115
9343.100
21.818
10.000
22.500
kg/m3
m
m2
m
kn
◦
All the relevant data for the wind heeling moment is given in table 5.1. The wind
itself is blowing from north-north-east at 18 knots, measured on a mountain near
Giglio at a height of over 600 metres [9]. Due to the boundary layer formed by
the wind over land and sea the wind velocity is lower in lesser heights. According
to the MODU Code design loads a wind velocity of 18 knots in over 256 metres
height is equivalent to 10 knots wind velocity at sea level, which is therefore used
here [6].
The floating position development with 10 knots of wind from the starboard
side is shown in figure 5.22, calculated with the same settings as in the reference
case. With the parameters given above, the wind moment is a little more than
half of the rock moment. Consequently, the draught and trim of the ship remain
the same as in the reference case but the heeling angle develops similar to the rock
moment case. Once again, the influence of the external moment begins to show
after four minutes, when the crew spaces in Compartment 4 on Deck A fill with
water. The final equilibrium however is now barely on the starboard side with an
heeling angle of circa 0.05 degrees.
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Draught [m], Trim [m], Heel [deg]
15
Draught reference
Trim reference
Heeling angle reference
Draught with wind from starboard
Trim with wind from starboard
Heeling angle with wind from starboard
10
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.22: Floating position development with wind from starboard
If the wind blows from port with the same velocity, the calculation yields the
floating position development in figure 5.23. Again, the wind moment comes into
play after 4 minutes but has little effect later on.
Draught [m], Trim [m], Heel [deg]
15
Draught reference
Trim reference
Heeling angle reference
Draught with wind from port
Trim with wind from port
Heeling angle with wind from port
10
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.23: Floating position development with wind from port
In both of the above calculations the wind does hit the side of the vessel at an angle
of 90 degrees. However, as the AIS track of the vessel in figure 5.24, this is not
the case in the real situation. Especially around the estimated time of the heeling
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10 k
not
s of
win
d
angle transition to starboard the wind blows almost from the front. Even during
the rest of the time the relative angle between ship and wind seldom exceeds 45 degrees. The wind velocity decreases with a trigonometric function depending on the
definition of the angles, while the wind moment decreases with the wind velocity
squared. Furthermore, the heeling moment of the drift force caused by the current
somewhat equalises the wind moment. Recognising the results of the calculations
performed above and taking into account the aforementioned effects, it is therefore
decided to exclude the wind moment from further calculations. Nevertheless, the
wind combined with the current and the rudder locked hard to starboard after the
blackout is vital for the turn and the drift ashore, which may have prevented a
much more severe development of the accident.
Figure 5.24: AIS track of M.V. Costa Concordia [10]
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5.2.3 Stabiliser Moment
As can be seen in several photos taken after the accident, the portside stabiliser of
the vessel is in a position, which would give maximum lift to starboard. Therefore,
the influence of the stabilisers is to be investigated as well. The heeling moment
for a pair of stabilisers is given by [1]:
ρ
MStabi = 2 · v 2 A · CL · R
2
(5.1)
In there, ρ denotes the density of sea water, v the speed of the vessel and A the
area of each stabiliser fin. The dimensions of one fin are estimated using photos
and the bulkhead plan to 5.8 metres by 2.32 metres. CL is the lift coefficient of the
stabiliser profile. It is set to 3 based on a conservative two-dimensional view and
an angle of attack of approximately 30 degrees. R finally is the distance between
the centre of lift on the profile and the centre of the waterline, which gives the
lever arm for the stabiliser moment. It amounts to half of the ships breadth plus
a conservative estimation of half the stabilisers breadth.
Using the given formula with the ships speed taken from the AIS, which is shown
in figure 5.25, this yields the heeling moment of the stabilisers in the same figure.
Heeling moment [tm]
1400
Stabiliser moment
Ship speed
16
14
1200
12
1000
10
800
8
600
6
400
4
200
2
Speed [kn]
1600
0
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.25: Ship speed and stabiliser moment according to AIS track [10]
It is currently unclear if the stabilisers were extended during the collision because
the weather conditions were good. Due to the movement of the vessels stern to
port before the contact with the rocks the stabilisers would not have been damaged
by the first ground contact. In any case, they would have not started to act until a
certain heeling angle was reached. Therefore, the stabiliser moment is modelled as
shown in the picture with no heeling moment at start and maximum lift from the
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first AIS time index after the collision onwards. With decreasing speed of course
the heeling moment decreases as well up to a point where it practically vanishes.
Draught [m], Trim [m], Heel [deg]
15
Draught reference
Trim reference
Heeling angle reference
Draught with stabiliser
Trim with stabiliser
Heeling angle with stabiliser
10
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.26: Floating position development with stabiliser
Using the described time-dependent stabiliser moment, the floating position of the
vessel develops as shown in figure 5.26 compared to the reference case. In this
figure the only recognisable difference is even lower than in the case with 10 knots
of wind from port. It is thus very likely, that any efforts of the stabilisers to upright
the ship would have been hindered by the wind blowing from starboard. In this
way, these two influences could have cancelled each other out during the initial
phases of the flooding.
In the final position of the vessel shown in figure 5.27, the starboard stabiliser
is certainly destroyed, so that the hydraulic pressure needed to operate the fins is
lost. Hence it could be possible, that the position of the portside stabiliser visible
in the photos is due to this pressure loss. Furthermore, it is unknown, to what
extent the stabilisers could actually be operated after the blackout. It is therefore
decided to exclude the stabiliser moment from any further calculations.
Figure 5.27: Position of portside stabiliser after the accident [10]
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5.2.4 Watertight Door 6
According to the VDR data, four watertight doors in the damage zone have been
opened and closed after the accident, as presented in table 4.5. In the following,
the influence of the opening and closing (hereafter denoted “activation”) of these
doors shall be investigated individually for each door using the same settings as in
the reference case.
Figure 5.28: Watertight Door 6
The first door to be examined is Watertight Door 6 on Deck C marked in figure
5.28, which connects the port Forward Engine Room in Compartment 7 with the
Sewage Room in Compartment 8. As can be seen in figure 5.29, this door is opened
43 seconds after the accident to 65 per cent, reaches a maximum volume flux of
about 250 cubic metres per minute and is again fully closed from 69 seconds on.
250
Flux through WTD 6
Volume flux [m3/min]
200
150
100
50
0
20:45:00
20:45:20
20:45:40
20:46:00 20:46:20
UTC [H:M:S]
20:46:40
20:47:00
Figure 5.29: Volume flux through Watertight Door 6
Approximately 55 cubic metres of water enter through Watertight Door 6 into
the Sewage Room, which is not much compared to the volumes in the rooms of
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Compartment 7, which are presented in figure 5.30.
2000
1800
1600
Volume [m3]
1400
Forward Diesel Engines port
Forward Diesel Engines Stairs
Forward Diesel Engines starboard
Lube Oil Purifiers Room
Engine Workshop
Sewage Room
1200
1000
800
600
400
200
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.30: Water volumes in Compartments 7 and 8 with activation of WTD 6
Due to the layout of the Sewage Room the water spreads over the whole breadth of
the ship. Consequently, even this little amount of water still leads to a significant
heeling moment of approximately 750 metre tonnes, as shown in figure 5.31.
15000
Heeling moment [tm]
10000
5000
Forward Diesel Engines port
Forward Diesel Engines Stairs
Forward Diesel Engines starboard
Lube Oil Purifiers Room
Engine Workshop
Sewage Room
0
-5000
-10000
-15000
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.31: Heeling moments of Compartments 7 and 8 with activation of WTD
6
The floating position development with the activation of Watertight Door 6 is
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pictured in figure 5.32. Once again, the additional heeling moment is effective
after four minutes, when the crew spaces on Deck A flood. However, due to the
extra flooded room the stability of the vessel is decreased and the heeling therefore
changes with a steep gradient to starboard after 14 minutes. The ship then comes
to an equilibrium with about 1.2 degrees angle of heel.
Draught [m], Trim [m], Heel [deg]
15
Draught reference
Trim reference
Heeling angle reference
Draught with WTD 6
Trim with WTD 6
Heeling angle with WTD 6
10
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.32: Floating position development with activation of WTD 6
5.2.5 Watertight Door 9
Figure 5.33: Watertight Door 9
The next door under investigation is Watertight Door 9 marked in figure 5.33,
leading from the Electric Motors Room in Compartment 5 to the Refrigeration
Compressors Room in Compartment 4 on Deck C. These rooms are both affected
by large leaks, so no large influence of this door activation is to be expected. Again,
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the same assumptions as in the reference case apply for the calculation of this door
activation. The door is opened 11 seconds after the rock contact to 55 per cent.
During this activation, the volume flux comes up to 430 cubic metres per minute,
as indicated in figure 5.34, until the door is closed at 33 seconds into the accident.
450
Flux through WTD 9
400
Volume flux [m3/min]
350
300
250
200
150
100
50
0
20:45:00
20:45:20
20:45:40
20:46:00 20:46:20
UTC [H:M:S]
20:46:40
20:47:00
Figure 5.34: Volume flux through Watertight Door 9
3000
2500
Volume [m3]
2000
Electric Motors reference
Refrigeration Compressors reference
Deck A Crew 11.1 reference
Deck A Crew 11 Corridor reference
Electric Motors with WTD 9
Refrigeration Compressors with WTD 9
Deck A Crew 11.1 with WTD 9
Deck A Crew 11 Corridor with WTD 9
1500
1000
500
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.35: Water volumes in Compartments 4 and 5 with activation of WTD 9
Figures 5.35 and 5.36 compare the reference case with the activation of Watertight
Door 9. There is not much difference between these two cases. The only effect
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is a little accelerated filling of the Refrigeration Compressors Room because the
opening of the door bypasses the leak in this room, which is obstructed by the
rock. This acceleration however is merely noticeable because there are only about
80 cubic metres of water exchanged.
10000
Electric Motors reference
Refrigeration Compressors reference
Deck A Crew 11.1 reference
Deck A Crew 11 Corridor reference
Electric Motors with WTD 9
Refrigeration Compressors with WTD 9
Deck A Crew 11.1 with WTD 9
Deck A Crew 11 Corridor with WTD 9
Heeling moment [tm]
8000
6000
4000
2000
0
-2000
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.36: Heeling moments of Compartments 4 and 5 with activation of WTD
9
Draught [m], Trim [m], Heel [deg]
15
Draught reference
Trim reference
Heeling angle reference
Draught with WTD 9
Trim with WTD 9
Heeling angle with WTD 9
10
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.37: Floating position development with activation of WTD 9
Because the local influence of the door activation is already small, the global
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influence is even smaller, as figure 5.37 shows, so that the activation of Watertight
Door 9 could be excluded from the model. However, there may be more complex
interactions due to effects not considered in this simple evaluation of its influence.
Therefore, Watertight Door 9 will be considered in further calculations.
5.2.6 Watertight Door 10
Figure 5.38: Watertight Door 10
Another door that has been opened after the accident is Watertight Door 10,
which connects the Refrigeration Compressors Room in Compartment 4 to the
Aft Auxiliary Room in Compartment 3 on Deck C, as marked in figure 5.38. The
Aft Auxiliary Room then leads to large void spaces on both sides of the ship.
This door is fully opened 41 seconds after the collision and is again closed from 86
seconds onwards. Figure 5.39 shows that during the 5 seconds it is fully open the
flux reaches about 800 cubic metres per minute.
800
Flux through WTD 10
Volume flux [m3/min]
700
600
500
400
300
200
100
0
20:45:00
20:45:20
20:45:40
20:46:00 20:46:20
UTC [H:M:S]
20:46:40
20:47:00
Figure 5.39: Volume flux through Watertight Door 10
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The total amount of water rushing through the door adds up to approximately
350 cubic metres, as is to be seen in figure 5.40. This is again not much compared
to the other rooms involved, but it is sufficient to have the greatest influence of all
watertight doors on the heeling moments so far, which is shown in figure 5.41.
2000
1800
1600
Volume [m3]
1400
Refrigeration Compressors
Deck A Crew 11.1
Deck A Crew 11 Corridor
Aft Auxiliary Room
Void Space 7 port
Void Space 7 starboard
1200
1000
800
600
400
200
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.40: Water volumes in Compartments 3 and 4 with activation of WTD 10
8000
7000
Heeling moment [tm]
6000
5000
Refrigeration Compressors
Deck A Crew 11.1
Deck A Crew 11 Corridor
Aft Auxiliary Room
Void Space 7 port
Void Space 7 starboard
4000
3000
2000
1000
0
-1000
-2000
-3000
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.41: Heeling moments of Compartments 3 and 4 with activation of WTD
10
This influence becomes even clearer in the floating position development as per
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figure 5.42. Due to the newly flooded compartment being positioned aft of the
damage zone, draught and trim are visibly increased compared to the reference
case. The additional water changes the time-dependent flooding of the other rooms
especially in Compartment 4 so that the heeling angle now swings through and
comes to an equilibrium at a higher value.
Draught [m], Trim [m], Heel [deg]
15
Draught
Trim
Heeling angle
Draught with
Trim with
Heeling angle with
10
reference
reference
reference
WTD 10
WTD 10
WTD 10
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.42: Floating position development with activation of WTD 10
5.2.7 Watertight Door 24
Figure 5.43: Watertight Door 24
The last door activated near the damage zone after the accident is Watertight
Door 24, which leads from Crew Space 11 in Compartment 4 to Crew Space 12 in
Compartment 3 on Deck A and is marked in figure 5.43. According to the Italian
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investigators the bulkhead of Watertight Door 24 was deformed resulting in a
leakage through this door. Here, only the activation of the door will be analysed,
while the leak is considered in the most likely scenario further down. Figure 5.44
shows the smallest flux through this watertight door as checked against the others
due to its high position on Deck A. Although this door is fully opened 4 minutes
and 45 seconds into the incident, it reaches only 90 cubic metres per minute before
the door is closed again after 5 minutes and 25 seconds.
100
Flux through WTD 24
90
Volume flux [m3/min]
80
70
60
50
40
30
20
10
0
20:45:00
20:46:00
20:47:00
20:48:00 20:49:00
UTC [H:M:S]
20:50:00
20:51:00
Figure 5.44: Volume flux through Watertight Door 24
600
500
Volume [m3]
400
300
Deck A Crew 11.1
Deck A Crew 11.2
Deck A Crew 11.3
Deck A Crew 11.4
Deck A Crew 11.5
Deck A Crew 11 Corridor
Deck A Crew 12.1
Deck A Crew 12.2
Deck A Crew 12 Corridor
200
100
0
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.45: Water volumes in Compartments 3 and 4 with activation of WTD 24
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Consequently, the water volumes in the newly flooded rooms shown in figure 5.45
only add up to about 30 cubic metres. Because Crew Space 12 stretches across
the whole starboard side of the vessel, it nevertheless leads to significant heeling
moments and thereby controls the spread of water in Crew Space 11, as shown in
figure 5.46.
2000
Deck A Crew 11.1
Deck A Crew 11.2
Deck A Crew 11.3
Deck A Crew 11.4
Deck A Crew 11.5
Deck A Crew 11 Corridor
Deck A Crew 12.1
Deck A Crew 12.2
Deck A Crew 12 Corridor
1500
Heeling moment [tm]
1000
500
0
-500
-1000
-1500
20:45 20:47 20:49 20:51 20:53 20:55 20:57 20:59 21:01 21:03 21:05
UTC [H:M]
Figure 5.46: Heeling moments of Compartments 3 and 4 with activation of WTD
24
Draught [m], Trim [m], Heel [deg]
15
Draught
Trim
Heeling angle
Draught with
Trim with
Heeling angle with
10
reference
reference
reference
WTD 24
WTD 24
WTD 24
5
0
-5
-10
-15
20:45
20:50
20:55
21:00
21:05 21:10
UTC [H:M]
21:15
21:20
21:25
Figure 5.47: Floating position development with activation of WTD 24
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The flooding of the starboard crew spaces in Compartment 3 enabled by the activation of Watertight Door 24 accelerates the transition of heel to the starboard
side, as can clearly be seen in figure 5.47. The additional flood water is to little
to affect draught and trim, but increases the heeling angle in the final equilibrium
by a small amount.
The quantities of water exchanged between the affected compartments through
the four watertight doors near the damage zone are summarised in table 5.2. The
lower and the further aft a door is positioned, the greater is the amount of water
passing through it due to the higher water head enabling the flow. As has been
shown above, the influence of an opened watertight door does not necessarily
depend on the duration of its activation, but rather on the interaction between the
position of the door and the development of the overall flooding.
Table 5.2: Water exchanged through watertight doors
WTD Exchanged
volume [m3 ]
From
compartment
Into
compartment
Deck
Time
[s]
6
9
10
24
7
5
4
4
8
4
3
3
C
C
C
A
26
22
45
40
55
80
350
30
It is once again pointed out that in each of the cases investigated up to here every
non-watertight door does not leak, which enables the equilibria. Furthermore, in
the case of Watertight Door 24 there is a leak reported due to a deformation of
the corresponding bulkhead, which lets water into Compartment 3 after the door
has been closed. This leak has not been considered up to here but will now be
investigated together with leaking non-watertight doors in the most likely scenario.
5.3 Most Likely Scenario
5.3.1 Overview
All of the effects investigated individually above will now be combined to simulate
the most likely scenario. The two exceptions to this are wind and stabilisers,
whose influence on the heeling angle is deemed too little and too discontinuous,
see sections 5.2.2 and 5.2.3. All watertight doors are activated as given in the
VDR, including the ones outside the damage zone. In addition, non-watertight
doors, such as fire doors or lift doors, are from here on modelled to leak according
to experiments performed in the FLOODSTAND project [15].
Leaking through these doors is either dependent or independent on the pressure
head acting on the door, as figure 5.48 demonstrates. This is because in some
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cases there is already a gap in the door and in other cases a gap is pushed open
by the pressure. Water only leaks through a small percentage of the door, until
the collapsing pressure height is reached and the opening breaks. Table 5.3 shows
these values for the most common opening types.
Aratio [-]
Aratio [-]
Type 1
1.0
Type 2
1.0
Aleak
Hcollapse H [m]
Aleak
Hcollapse H [m]
Figure 5.48: Leaking types
Table 5.3: Leaking values of different openings [15] [12]
Opening type
Leaking type
Aleak
Elevator door
Single fire door
Double fire door
Cold store door
1
2
1
2
0.035
0.025
0.025
0.010
Watertight and splashtight doors do not leak, while they are not opened. There
is however one exception to this rule, which is Watertight Door 24. According
to the Italian investigators, this door was observed to leak by witnesses due to a
deformation of the related watertight bulkhead during the collision. Because the
amount of water entering through Watertight Door 24 is unknown, the leaking
area ratio will be determined in such a way, that the floating position at the time
of dropping the starboard anchor shown in figure 5.49 is reached. This means a
heeling angle of around 14 degrees and a trim of around 5.2 metres at the time of
21:48 UTC or 3773 seconds simulation time.
The leaking ratio of Watertight Door 24 derived by this approach amounts to
0.024, which is in the order of magnitude of the values in table 5.3. With this
value and all other mentioned settings, the simulation yields the floating position
shown in figure 5.50 after 3773 seconds. Using the submergence of the windows as
a reference point, it can be seen that this floating position is the same as in the
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one in figure 5.49, although the values of heel and trim differ a little from the ones
calculated in the photogrammetric expertise.
Figure 5.49: M.V. Costa Concordia at 21:48 UTC (Source: Giglio News)
Figure 5.50: Floating position at 21:48 UTC in the most likely scenario
Figure 5.51 shows the development of the floating position in the most likely scenario till the time of the second grounding compared to the reference case. The
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flooding process will now be explained and checked with the timeline in table 3.2.
Draught [m], Trim [m], Heel [deg]
15
10
5
0
-5
Draught reference
Trim reference
Heeling angle reference
Draught in most likely scenario
Trim in most likely scenario
Heeling angle in most likely scenario
-10
-15
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.51: Floating position development in the most likely scenario
Due to the rock moment and the flood water rushing in, the initial heel is as
expected to port. The final blackout after 108 seconds coincides well with the
flooding of the starboard Main Switchboard Room in Compartment 6 shown in
figure 5.52, which is confirmed by the crew around five minutes later. During this
time the ship heels about 10 degrees to port, which is in the expected range. The
blackout did also disable any pumps that could have been used to mitigate the
flooding, which are thus not considered in the calculations.
MSR ps
MSR sb
Figure 5.52: Main switchboard rooms at the time of the blackout
5.3.2 Influence of the Damaged Compartments
The other rooms of the switchboard Compartment 6 are due to their size very
decisive in the initial phase of the flooding, as figures 5.53 and 5.54 show. This
size remains important in the later phase, when the heel changes to starboard.
Although there is not much space for the water to change position, the sheer mass
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leads to significant heeling moments with increasing heeling angle, especially by
the Incinerators Room on the starboard side. The portside Aft Engine Room
contributes to this effect later on, when upper corners of this room emerge above
the waterline and the room empties, so that the water can move more freely.
6000
Water Ballast DB 12C
Aft Diesel Engines port
Aft Diesel Engines starboard
Incinerators Room
Main Switchboard Room port
Main Switchboard Room starboard
Sum
5000
Volume [m3]
4000
3000
2000
1000
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.53: Water volumes in Compartment 6 in the most likely scenario
25000
Water Ballast DB 12C
Aft Diesel Engines port
Aft Diesel Engines starboard
Incinerators Room
Main Switchboard Room port
Main Switchboard Room starboard
Sum
Heeling moment [tm]
20000
15000
10000
5000
0
-5000
-10000
-15000
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.54: Heeling moments of Compartment 6 in the most likely scenario
Compartment 7 is the second one to be confirmed flooded by the crew. This one
takes much longer to flood due to the much smaller leak, as is to be seen in figure
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5.55. Again, edges of the portside rooms emerge above the waterline when the
heel to starboard increases. This influence is shown in a faster decreasing heeling
moment of these rooms as per figure 5.56. Because of its central position on Deck
A, the Engine Workshop is the last room to become flooded and is responsible for
the lowest heeling moment in this compartment.
4500
Water Ballast DB 11C
Forward Diesel Engines port
Forward Diesel Engines Stairs
Forward Diesel Engines starboard
Lube Oil Purifiers Room
Engine Workshop
Sum
4000
3500
Volume [m3]
3000
2500
2000
1500
1000
500
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.55: Water volumes in Compartment 7 in the most likely scenario
15000
Water Ballast DB 11C
Forward Diesel Engines port
Forward Diesel Engines Stairs
Forward Diesel Engines starboard
Lube Oil Purifiers Room
Engine Workshop
Sum
Heeling moment [tm]
10000
5000
0
-5000
-10000
-15000
-20000
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.56: Heeling moments of Compartment 7 in the most likely scenario
Fifteen minutes after the collision Compartment 5 is also reported to be flooded,
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although the flooding itself takes only a few minutes as stated in the official investigation. This compartment mainly consists of the Electric Motors Room, which
spreads across the whole breadth of the ship and thus governs the influence on
mass and heeling moment, as illustrated in figures 5.57 and 5.58. The portside
Synchroconverter Room empties as the vessel heels to starboard, which reduces
the corresponding heeling moment.
3500
Void Space DB 6C
Electric Motors
Synchroconverter Room port
Synchroconverter Room starboard
Sum
3000
Volume [m3]
2500
2000
1500
1000
500
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.57: Water volumes in Compartment 5 in the most likely scenario
12000
Void Space DB 6C
Electric Motors
Synchroconverter Room port
Synchroconverter Room starboard
Sum
10000
Heeling moment [tm]
8000
6000
4000
2000
0
-2000
-4000
-6000
-8000
-10000
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.58: Heeling moments of Compartment 5 in the most likely scenario
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35
Flux through WTD 24
Volume flux [m3/min]
30
25
20
15
10
5
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.59: Volume flux through Watertight Door 24 in the most likely scenario
Because Watertight Door 24 has a leak as described above in the most likely
scenario, the volume flux develops over time as shown in figure 5.59. It reaches
about one third of the volume flux during the short full opening and closing of
this door, what shows as a peak in this time-scale. As in the reference case, the
crew spaces in front of Watertight Door 24 are flooded via an escape trunk to the
Refrigeration Compressors Room.
3000
2500
Volume [m3]
2000
1500
Refrigeration Compressors
Service Lift aft port
Service Lift aft starboard
Deck A Crew 11.1
Deck A Crew 11.2
Deck A Crew 11.3
Deck A Crew 11 Corridor
Staircase MFZ 1+2
Sum
1000
500
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.60: Water volumes in Compartment 4 in the most likely scenario
The most influential ones of these crew spaces are once again the corridor between
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the cabins as well as the outermost cabins (11.1), as figures 5.60 and 5.61 show. The
latter are even more important than the large Refrigeration Compressors Room
during the later phases of the accident.
8000
6000
Heeling moment [tm]
4000
2000
0
-2000
-4000
-6000
-8000
-10000
20:45
Refrigeration Compressors
Service Lift aft port
Service Lift aft starboard
Deck A Crew 11.1
Deck A Crew 11.2
Deck A Crew 11.3
Deck A Crew 11 Corridor
Staircase MFZ 1+2
Sum
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.61: Heeling moments of Compartment 4 in the most likely scenario
The additional free surfaces in the compartments now flooded through Watertight
Doors 6 and 10 affect the time-dependent flooding in these crew spaces, which together explains the greater heeling angles to port before the transition to starboard
as compared to the reference case.
600
Water Ballast DB 10C
Sewage Room
Sum
500
Volume [m3]
400
300
200
100
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.62: Water volumes in Compartment 8 in the most likely scenario
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One of these is Compartment 8, which is only flooded in the double bottom through
the scratch at frame 116 and by the activation of Watertight Door 6 in the Sewage
Room, illustrated in figures 5.62 and 5.63. The heeling moment of the double
bottom tank almost vanishes as soon as it is full due to the symmetric layout.
In the Sewage Room on the other hand a dangerous free surface remains, which
contributes to the fast passing from port to starboard.
5000
Water Ballast DB 10C
Sewage Room
Sum
Heeling moment [tm]
4000
3000
2000
1000
0
-1000
-2000
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.63: Heeling moments of Compartment 8 in the most likely scenario
5.3.3 Heel Change to Starboard
In addition to the spaces stretching across the whole breadth, which were flooded
through Watertight Doors 6 and 10 in the most likely scenario and thus have large
free surfaces, the change of heel to starboard is enabled by two other effects. One
of these is the leak in Watertight Door 24, which primarily floods the crew spaces
on the starboard side of Deck A in Compartment 3 and from there on upwards
onto the freeboard deck via the paths marked blue in figure 5.64. The water is
hindered to flow to port because the door to the Buffet Preparation on the port side
marked red in the same figure is closed and thus only leaks a bit. Another opening
that helps towards the starboard heel is the one connecting the Incinerators Room
on Deck C to the Garbage Plant on Deck 0 marked in figure 5.65, which is also
located on the far starboard side and one of the openings responsible for progressive
flooding. The temporary righting lever curve at the time of the heel change shows
a minimum metacentric height of around 0.7 metres. All of the mentioned effects
are then enough to compensate for the rock moment heeling to port and finally
change the heel to starboard. The transition of the heeling angle in the simulation
happens about 18 minutes after the accident, a little bit earlier than estimated
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for the real situation. According to the AIS track, the wind, which has not been
considered in this calculation, would blow almost from the front on the port side
of the vessel at both times and would thus have only a marginal influence on the
heel change to starboard, if any. However, there is no exact time of the heel change
stated in the report and the difference between the estimation and this calculation
is only a few minutes, so that the sinking simulation is deemed acceptable in this
regard.
Workshops pt
Buffet Preparation
Deck A Crew 11
Workshops ct
Staircase MFZ 1+2
Aft Staircase
Workshops sb
Deck A Crew 12
Figure 5.64: Deck A in Compartment 3 [12]
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Cold Room 3
Cold Room 1
Exhaust Shaft
Cold Room 4
Cold Room 2
Air Con. Shaft
5
Garbage Plant
Figure 5.65: Garbage Plant on Deck 0 [12]
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5.3.4 Influence of the Undamaged Compartments
900
800
700
Volume [m3]
600
500
Aft Auxiliary Room
Void Space 7 port
Void Space 7 starboard
Deck A Buffet Preparation
Deck A Crew 12.1
Deck A Crew 12.2
Deck A Crew 12 Corridor
Sum
400
300
200
100
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.66: Water volumes in Compartment 3 in the most likely scenario
Compartment 3 is decisive because of two watertight doors leading to it on Deck
C and Deck A, which were opened or leaking, namely Watertight Doors 10 and 24.
As figures 5.66 and 5.67 show, the Aft Auxiliary Room and void spaces on Deck
C are flooded first through Watertight Door 10, while the mentioned crew spaces
on Deck A become filled continuously later on through Watertight Door 24.
4000
Heeling moment [tm]
2000
0
-2000
-4000
-6000
-8000
-10000
20:45
Aft Auxiliary Room
Void Space 7 port
Void Space 7 starboard
Deck A Buffet Preparation
Deck A Crew 12.1
Deck A Crew 12.2
Deck A Crew 12 Corridor
Sum
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.67: Heeling moments of Compartment 3 in the most likely scenario
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During the heeling angle transition water is exchanged rapidly between the two
void spaces. The increasing heeling moment is then determined by the starboard
Void Space 7 and the starboard outermost crew cabins (12.1). Because the portside
Buffet Preparation is only slowly flooded through a leaking fire door, its effect is
not notable.
250
Volume [m3]
200
150
Aft Thruster Room
Void Space 8 port
Void Space 8 starboard
Deck A Workshops port
Deck A Workshops center
Aft Staircase
Deck A Workshops starboard
Sum
100
50
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.68: Water volumes in Compartment 2 in the most likely scenario
500
Heeling moment [tm]
0
-500
-1000
-1500
-2000
-2500
-3000
-3500
20:45
Aft Thruster Room
Void Space 8 port
Void Space 8 starboard
Deck A Workshops port
Deck A Workshops center
Aft Staircase
Deck A Workshops starboard
Sum
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.69: Heeling moments of Compartment 2 in the most likely scenario
Compartment 2 is mainly flooded through the Aft Staircase, which connects it
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to the crew spaces of Compartment 3 on Deck A. As can be seen in figures 5.68
and 5.69, the water in the staircase first needs to rise to Deck 0 before it can
surpass the bulkhead between the two compartments after 48 minutes and flow
into the workshops on the starboard side of Deck A. While these workshops exert
significant heeling moments, the other rooms in this compartment do not play any
role.
Cold Room 2
Cold Room 4
Cold Room 6
Cold Room 8
Cold Room Corridor
Cold Room 10
Steering
Gear sb
Cold Room 1
Aft Corridor
Staircase
MFZ 1+2
Aft Staircase
Exhaust Shaft
Air Con. Shaft
Dry Store
Cold Room 3
Cold Room 5
Cold Room 7
Steering
Gear pt
Cold Room 9
5.3.5 Progressive Flooding of Deck 0
Garbage Plant
Aft Tender Emb. sb
Figure 5.70: Rooms on the freeboard deck (Deck 0) [12]
Forty minutes into the accident, the crew reports water on the freeboard deck, Deck
0, specifically from the aft Service Lifts and from the fire doors to the staircase of
main fire zone 1 and 2 marked yellow in figure 5.70. The progressive flooding in
the simulation starts some time prior to this with water entering into the Garbage
Plant, Cold Room 4 and Tender Embarkation Station marked red in the same
figure. The difference between the crew statements and the sinking simulation can
be explained by the fact, that water accumulating in these rooms is not directly
visible from one point of view and that the compartment model is not an exact
replica of the real rooms.
Figure 5.71 shows the fluxes through the openings into these rooms, which start
shortly before the heeling angle transition to starboard. The vital role of the
starboard opening connecting the flooded Incinerators Room with the Garbage
Plant is obvious from this picture. The doors connecting the Garbage Plant to
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the rest of Deck 0 are all closed and far enough midships so that it takes some
time to further flood the ship from here. Water entering Cold Room 3 on the port
side immediately flows into the Aft Corridor on Deck 0 and from there into the
starboard Aft Tender Embarkation Station, until the latter is full. Cold Room 4
on the starboard side becomes flooded via two openings before the water level is
high enough to enter the next cold room further forward.
35
Incinerators Room to Garbage Plant
Service Lift aft port to Cold Room 3
Service Lift aft starboard to Cold Room 4
Staircase MFZ 1+2 to Cold Room 4
Staircase MFZ 1+2 to Aft Corridor
Volume flux [m3/min]
30
25
20
15
10
5
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.71: Volume fluxes due to progressive flooding
In the following, the spread of water on Deck 0 is shown and discussed. As mentioned above, one of the first rooms to flood above the freeboard deck is the
starboard Aft Tender Embarkation Station. In the aft area of Deck 0 it remains
the only room with water in it till about 30 minutes after the collision, as figures
5.72 and 5.73 demonstrate. Then the large Aft Corridor, which connects most of
the rooms in the affected area, begins to fill up and at some time exceeds mass and
heeling moment of the Tender Embarkation Station. The Cold Room Corridor,
which is the space between the open Splashtight Doors 8 and 9 and leads to Cold
Room 8, does not have much influence, so that the closure of the named doors
would not have either. Any other rooms in this vicinity do not become flooded
that much.
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400
350
Volume [m3]
300
250
Aft Corridor
Aft Tender Embarkation starboard
Cold Room Corridor
Cold Room 8
Cold Room 10
Steering Gear Room starboard
Dry Store
Sum
200
150
100
50
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.72: Water volumes on deck 0 in the most likely scenario, part 1
1000
Heeling moment [tm]
0
-1000
-2000
-3000
-4000
-5000
-6000
20:45
Aft Corridor
Aft Tender Embarkation starboard
Cold Room Corridor
Cold Room 8
Cold Room 10
Steering Gear Room starboard
Dry Store
Sum
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.73: Heeling moments of deck 0 in the most likely scenario, part 1
The volume and heeling moment of the cold rooms further forward on Deck 0 is
plotted in figures 5.74 and 5.75. This is done in comparison with the Aft Corridor
and also with the lifts and staircase, through which Deck 0 is progressively flooded.
Due to the direct access Cold Room 4 is flooded first, while Cold Rooms 2 and 6
also on the starboard side begin to take on water 18 minutes later. In the case of
Cold Room 2 this happens via an opening to Cold Room 4, the smaller Cold Room
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6 is flooded from the Aft Corridor. The rooms with vertical extension enabling
the progressive flooding do not have that much impact on the heel, which the
aforementioned cold rooms have due to their position on the starboard side.
900
800
700
Volume [m3]
600
500
Service Lift aft port
Service Lift aft starboard
Staircase MFZ 1+2
Aft Corridor
Cold Room 2
Cold Room 4
Cold Room 6
Sum
400
300
200
100
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.74: Water volumes on deck 0 in the most likely scenario, part 2
2000
Heeling moment [tm]
0
-2000
-4000
-6000
-8000
-10000
-12000
20:45
Service Lift aft port
Service Lift aft starboard
Staircase MFZ 1+2
Aft Corridor
Cold Room 2
Cold Room 4
Cold Room 6
Sum
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.75: Heeling moments of deck 0 in the most likely scenario, part 2
Of the last set of rooms on Deck 0 the most decisive one by far is the Garbage
Plant, as figures 5.76 and 5.77 illustrate. The Air Conditioning Shaft and the
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Exhaust Shaft, which are connected vertically to both engine rooms, as well as
the starboard Bunker Station near frame 116 take on some water, but exert even
lower heeling moments to starboard than the Aft Corridor.
900
800
700
Volume [m3]
600
Aft Corridor
Bunker Station
Air Conditioning Shaft
Exhaust Shaft
Garbage Plant
Sum
500
400
300
200
100
0
20:45
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.76: Water volumes on deck 0 in the most likely scenario, part 3
2000
Heeling moment [tm]
0
-2000
-4000
-6000
-8000
-10000
-12000
-14000
20:45
Aft Corridor
Bunker Station
Air Conditioning Shaft
Exhaust Shaft
Garbage Plant
Sum
20:55
21:05
21:15
21:25
UTC [H:M]
21:35
21:45
21:55
Figure 5.77: Heeling moments of deck 0 in the most likely scenario, part 3
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5.3.6 Second Grounding
The final position reached at 21:55 UTC, the time of the second grounding, is shown
in figure 5.78 for the real situation and in figure 5.79 for the sinking simulation in
the most likely scenario. As is to be seen in there, the floating positions match
each other as well as in the case of 21:48 UTC. The most likely scenario ends at
this time after 4193 seconds of simulation; grounding effects are discussed in a
separate section due to only limited information being available on the seabed.
Figure 5.78: M.V. Costa Concordia at 21:55 UTC (Source: Giglio News)
Figure 5.79: Floating position at 21:55 UTC in the most likely scenario
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5.4 Grounding Effects
Draught [m], Trim [m], Heel [deg]
The flooding simulation is at this time able to consider a flat seabed at a given
depth using a spring model as described in section 2.3. This limits the movements
of the vessel and can be used to investigate grounding effects. For this purpose,
the water depth has been adjusted in such a way, that the M.V. Costa Concordia comes into contact with the ground at 21:55 UTC in the most likely scenario.
This results in a seabed positioned 13.78 metres below the water surface, which is
modelled using spring elements of varying stiffness. Figure 5.80 shows the floating position development for three seabed stiffness values between 5 and 50 t/m.
Higher stiffness values lead to numerical problems and thus unrealistic results.
20
15
10
5
0
-5
-10
-15
20:45 21:15 21:45 22:15 22:45 23:15 23:45 00:15 00:45 01:15 01:45 02:15
UTC [H:M]
Draught with stiffness 5
Trim with stiffness 5
Heeling angle with stiffness 5
Draught with stiffness 25
Trim with stiffness 25
Heeling angle with stiffness 25
Draught with stiffness 50
Trim with stiffness 50
Heeling angle with stiffness 50
t/m
t/m
t/m
t/m
t/m
t/m
t/m
t/m
t/m
Figure 5.80: Floating position development while grounding
Until the time of the ground contact the curves are the same. After this period, the
vessel grounds with the starboard aft area of the hull, which results in a righting
moment exerted by the seabed and hence a decrease in heel. During this time
a weathertight door leading into the Aft Corridor collapses, which leads to the
increase in draught and trim. These two events interact and lead to a greater
contact area with the seabed, so that more force is applied in the aft area and the
further draught and trim development then depends on the stiffness. The higher
the stiffness, the greater are the acting forces and thus the less are draught and
trim later on, although the difference between the higher stiffness values is not
noteworthy.
In the case of these higher stiffness values the vessel is pushed upright quicker
because it cannot sink into the ground that far. This lets the flood water less time
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to govern the floating position development. Therefore, the final equilibrium is
on the starboard side in both cases with a floating position like pictured in figure
5.81.
Figure 5.81: Final floating position with a seabed stiffness of 50 t/m
With a stiffness of 5 t/m however this is not the case, as it allows the ship to sink
deeper, so that the aft passenger cabins on Deck 1 are flooded. This increases the
draught in such a way, that Compartment 9 marked in figure 5.82 is also flooded
by water surpassing the bulkhead to Compartment 8. All of these effects decrease
the stability of the vessel so much, that the heeling angle changes to port, where
the final equilibrium shown in figure 5.82 is reached.
In reality the higher stiffness values would be more appropriate because the
seabed at the grounding site consists mainly of rocks. With an even seabed as
assumed here the situation would have developed not as severe as it actually did.
However, the actual seabed is of a much more complex geometry. From what is
known after lifting the wreck, there are two main pinning points, with which the
vessel had contact. It is likely that the vessel was pushed sideways against these
points by wind and current, what would have led to a further heeling moment to
starboard. In that way the grounding would have deteriorated the situation as
opposed to the improvement with an even seabed.
Because the sinking simulation program does at this time only support an even
seabed and exact bathymetric data of the grounding site is not known to the
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grounding is performed here.
Compartment 9
Figure 5.82: Final floating position with a seabed stiffness of 5 t/m
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5.5 Hypothetical Scenarios
5.5.1 Sinking at Sea
In the most likely scenario the vessel grounds after some time and the floating
position development then depends mainly on the interaction with the seabed.
Therefore, the most likely scenario is once again calculated for a longer time without the consideration of grounding to see how the vessel would sink at the open
sea. This yields the floating position development shown in figure 5.83.
Draught [m], Trim [m], Heel [deg]
100
80
60
Draught in most likely scenario
Trim in most likely scenario
Heeling angle in most likely scenario
Draught while sinking at sea
Trim while sinking at sea
Heeling angle while sinking at sea
40
20
0
-20
20:45 20:55 21:05 21:15 21:25 21:35 21:45 21:55 22:05 22:15
UTC [H:M]
Figure 5.83: Floating position development while sinking at sea
The ship would have capsized about 90 minutes after the collision at the open sea,
20 minutes after she had grounded in the real event. The progression of the heeling
angle shows several knuckles, which result from the collapsing of critical openings.
These are marked in order of their collapsing in figure 5.84.
5.
3.
2.
1.
4.
Figure 5.84: Critical openings while sinking at sea
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All of these openings are large weathertight doors leading to likewise large rooms
on Deck 0, Deck 1 and Deck 2. Number 1 leads to the Aft Corridor and number
3 to the Forward Corridor on Deck 0, while number 2 connects the Forklift Area
on the same deck to the outside world. The collapsing of these openings results
in the first three visible knuckles of the heeling angle evolution. Number 4 and 5,
which together are responsible for the last knuckle before the steep increase of the
heeling angle, are positioned in the passenger cabins on Deck 1 and Deck 2.
01:22:16
01:24:12
01:24:28
01:24:52
Figure 5.85: Immersion of Deck 4 while sinking at sea
According to the official investigation, many of the victims were found in the aft
area on Deck 4 [10]. Figure 5.85 shows how this might be explained by capturing
a situation shortly before the capsize. Due to the collapsing of the aforementioned
critical openings the heeling angle increases by 15 degrees within merely two and
a half minutes. During this time Deck 4, which is the deck with access to the
lifeboats and is hence retracted, becomes quickly submerged and traps anyone on
it under Deck 5, which expands above Deck 4 up to the whole breadth.
In the real accident of course the grounding delays these events but a similar
failure mode is very likely. Therefore, the faster increase of the heeling angle after
the grounding as per table 3.2 could not be only due to the grounding moment
but also due to the collapse of some of the mentioned openings. It is however clear
from the results presented here, that this hypothetical scenario of sinking at sea
would have led to much more victims because of the much faster time to sink.
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5.5.2 No Leak in Watertight Door 24
As described above, the leak in Watertight Door 24 reported by the crew plays a
vital role for the change of heel to starboard and the further flooding process. This
is the case even though the leaking area ratio of this door determined in the most
likely scenario is only 0.024. The significance of this leak is therefore of special
interest, which shall now be investigated by keeping all the settings as in the most
likely scenario but by excluding the leak in Watertight Door 24 from the model.
Figure 5.86 demonstrates the floating position development in this case.
Draught [m], Trim [m], Heel [deg]
20
0
-20
-40
-60
-80
Draught in most likely scenario
Trim in most likely scenario
Heeling angle in most likely scenario
Draught without leak in WTD 24
Trim without leak in WTD 24
Heeling angle without leak in WTD 24
-100
20:45 21:00 21:15 21:30 21:45 22:00 22:15 22:30 22:45 23:00 23:15
UTC [H:M]
Figure 5.86: Floating position development without leak in Watertight Door 24
Interestingly, the missing leak in Watertight Door 24 now prevents the heel change
to starboard. This starts about 15 minutes after the collision, about the time, at
which the crew spaces in Compartment 3 on Deck A would begin to flood and
the flux through Watertight Door 24 would reach an almost constant value, see
figures 5.67 and 5.59. These events would lead to significant heeling moments to
starboard, which are consequently missing here. Furthermore, this has an effect on
the progressive flooding of the freeboard deck, which happens now with the ship
heeling to port and thus leads to sinking via the portside of the vessel. The aft trim
also takes more time to develop because the trimming moment of Compartment
3 and rooms progressively flooded from this compartment are now missing in the
earlier phase. After about two hours and 24 minutes the ship has capsized onto the
port side. Once again, this happens due to collapsing of the portside counterparts
of the aforementioned critical openings. Another calculation shows, that it would
take over 9 knots of wind pushing constantly on the port side to change the heel
to starboard in this scenario. All in all, the missing leak in Watertight Door 24
delays the capsize by about one hour and changes its direction to port.
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5.5.3 All Watertight Doors Closed
Draught [m], Trim [m], Heel [deg]
20
0
-20
-40
-60
-80
Draught in most likely scenario
Trim in most likely scenario
Heeling angle in most likely scenario
Draught with all watertight doors closed
Trim with all watertight doors closed
Heeling angle with all watertight doors closed
-100
20:45 21:15 21:45 22:15 22:45 23:15 23:45 00:15 00:45 01:15 01:45
UTC [H:M]
Figure 5.87: Floating position development with all watertight doors closed
As a last hypothetical scenario it is assumed that all watertight doors are closed
from the beginning and neither opened nor leaking thereafter, while everything
else is the same as in the most likely scenario. With these settings, the calculation
yields the floating position development in figure 5.87.
Again, the final capsize is onto the port side because of the missing influence of
the leak in Watertight Door 24 discussed above. In addition to this, the influence
of Watertight Doors 6 and 10 is recognisable. Due to about 350 tons of water
now missing in Compartment 3 on Deck C, which is positioned directly aft of the
damage zone and connected to it via Watertight Door 10, the trim does not increase
as fast as in the most likely scenario. This has an effect on the flooding of Deck 0
because with less trim there is less water head acting on the openings responsible
for progressive flooding and thus less volume flux through these openings. With
no water in the spaces stretching across the whole breadth of the ship, which
would enter both Compartments 3 and 8 through Watertight Doors 6 and 10 in
the most likely scenario, there is nothing to drastically change the heel. Therefore,
the heeling angle only slowly increases due to progressive flooding, until the vessel
capsizes via the failure mode described above.
Further studies have shown, that the calculation is rather sensitive on the leaking
types presented in figure 5.48. If for example all non-watertight doors are modelled
with a leaking type depending on the pressure head (Type 2 in figure 5.48), the
vessel would stay afloat more than twice the time as here with almost no heeling
angle and very slowly increasing draught and trim. This assumption would of
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course not be in line with the results of the FLOODSTAND project, but shows
how even small changes can have great effect, if they are effective long enough.
Figure 5.88: Floating position at 21:55 UTC with all watertight doors closed
The time to capsize with all watertight doors closed is over twice as long as it
would have been without the leak in Watertight Door 24 and over three times as
long compared to sinking at sea in the most likely scenario, namely a little over 5
hours. At the time of the second grounding in the real event, the vessel would take
the floating position in figure 5.88, if all watertight doors are closed. The shown
floating position with a bit less trim than in the real situation and almost even
heel would have made the evacuation much easier, because lifeboats could have
been used on both sides without problems.
These results show clearly, that it is vital to keep the watertight doors closed at
all times. If this is done, even a damage as severe as in the case of M.V. Costa
Concordia with 5 damaged compartments results in far enough time to evacuate.
In some cases, this might lead to wrong conclusions by the crew about the severity
of the flooding, so that an evacuation, which can be dangerous itself, might not be
performed. This changes however nothing of the fact, that even a timely limited
opening of watertight doors during a flooding can have devastating effects and is
thus to be avoided.
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CONCLUSION
6 Conclusion
Using a sinking simulation with a quasi-static approach in the time domain, the
sinking sequence of M.V. Costa Concordia has been successfully reconstructed.
During this reconstruction, the status of watertight doors has shown to be decisive
in several ways.
One effect is the flooding of undamaged spaces stretching across the whole
breadth of the ship, such as through Watertight Door 6 into the Sewage Room
in Compartment 8. In these spaces the water can move freely from side to side,
which decreases the stability of the vessel and determines the gradient of a possible
heel change. Another effect concerns the water entering rooms aft of the damage
zone, as for example from Compartment 4 into Compartment 3 through Watertight Door 10. Thereby the trim to aft is increased, so that the water head rises
at openings critical for progressive flooding. This results in higher volume fluxes
through these openings and thus in a faster sinking or capsizing.
The worst case however is a leak in a watertight door, which applies to Watertight Door 24 due to a deformation of the related watertight bulkhead during the
collision. On the one hand this breaches the watertight compartmentation below
the bulkhead deck, a situation the ship is not designed for by the statutory damage stability calculations. This circumvents the purpose of a watertight door by
constantly letting water into normally undamaged rooms. On the other hand the
layout of the rooms near the door can have a significant impact, as is the case with
M.V. Costa Concordia. Here, the additional flooded crew spaces in Compartment 3 on Deck A are centred on starboard, while the portside Buffet Preparation
is only slowly flooded through a closed but leaking fire door. Hence, primarily the
starboard side is flooded through Watertight Door 24, what has been shown to be
the decisive factor for the heel change to starboard.
From section 5.3 onwards, the rock moment is considered in each calculation.
This is a done via a shift of the transverse centre of gravity of the vessel by 11.8
millimetres to port, so that the final transverse centre of gravity is then almost
midships. Wind is neglected in the simulations because the velocity is only 10
knots and because the relative angle between ship and wind is too small and too
discontinuous. The most likely scenario, including the heel change to starboard,
could be reconstructed well without the influence of wind. If there would be any
influence, it would show as a decrease in the leaking area ratio of Watertight Door
24, which has been determined as 0.024. This is the case because wind alone
without a leaking Watertight Door 24 would not be enough to cause the floating
positions documented by photos in the given time. Nevertheless, wind together
with current is important to explain the drift ashore and the heeling moment caused
by the second grounding. The influence of stabilisers is also not considered because
it is not that great and because the reliable operation of the fins is uncertain.
As to any grounding effects, only an even seabed could be investigated. With this
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CONCLUSION
assumption, the final equilibrium after grounding then depends on the stiffness of
the seabed. Independent of the seabed stiffness, the heeling angle decreases, while
draught and trim increase, as the vessel comes to rest on the ground. This shows,
that an even seabed would have improved the real situation by supporting the
ship. Unfortunately, in the actual accident the ship was pinned onto two rocks by
wind and current, which increased the heel until the M.V. Costa Concordia
capsized.
Finally the most likely scenario has been simulated until the capsize and compared to a similar simulation with all watertight doors closed. In the latter scenario
it takes more than three times as long to reach 90 degrees of heel, while the capsize
direction changes from starboard to port. This would have been very beneficial
for the evacuation and shows the importance of closed watertight doors. But this
shows also, that even the closure of all watertight doors could not have prevented
sinking. Five damaged compartments are just too much compared to the survivability of two damaged compartments as required by the SOLAS rules applying
for M.V. Costa Concordia.
The whole flooding is a complex non-linearly coupled process involving many
rooms and openings, which can respond very differently to even small changes.
Furthermore, a simulation of the flooding process suffers from several inaccuracies
and has to be based on empirical parameters, such as the discharge coefficients,
leaking area ratios and collapsing pressure heights. Since these limitations apply
for all of the calculated scenarios, proper conclusions can be drawn from the differences between them.
The most obvious conclusion is of course, that watertight doors are to be kept
closed at all times. Even a temporary opening of such a door during a flooding,
for example to enable an escape from a damaged compartment, can have severe
consequences. For the purpose of escape it is better to fit additional vertical
escape trunks, although these need to be designed in such a way that entering
water does not block access to them. Such escape trunks however can also be
problematic due to upflooding. This leads to the next conclusion, which is the
limitation of up- and thereby progressive flooding. As is evident from the most
likely scenario, there are only a few openings responsible for progressive flooding,
but these are enough due to their size and position. Therefore, openings in the
freeboard deck need to be further reduced in number and possibly made watertight
as well, although this might lead to similar problems as with watertight doors. The
final conclusion is thus to also limit the number of watertight doors during the ship
design process. This is underlined by the fact, that the leak in Watertight Door
24 is only possible due to the natural gap between door and bulkhead, whose
sealing is made ineffective by the deformation of the bulkhead. Watertight Door
24 for example is only needed to enable passing from the Buffet Preparation in
Compartment 3 to the aft Service Lifts in Compartment 4 on Deck A. If the
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CONCLUSION
Buffet Preparation would have been moved into Compartment 4, Watertight Door
24 would not have been necessary, so that it could not have leaked during the
accident.
But no matter how much effort is put into ship safety by the IMO and designers,
it all accounts to nothing, if the operation of a ship is not performed well. From an
engineering point of view, it is possible to further subdivide a ship longitudinally,
transversely and vertically to increase the damage stability. Such an approach
however becomes easily so expensive, that even modern navies do not hold it
up anymore. In addition, a finer subdivision requires more watertight doors for
practical reasons, which again lead to the mentioned problems. Therefore, it is
the responsibility of the crew to avoid any dangerous situation in the first place
because a possible damage does not know its maximum extension per SOLAS.
And one thing remains certain: a leak the size of the ship will sink it.
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References
References
[1] Abdel-Maksoud, M. (2010). Skriptum zur Vorlesung Seeverhalten von Schiffen.
Lecture Notes, Hamburg University of Technology.
[2] Culjak, A. (2013). Organisation und Devianz - Eine empirische Fallrekonstruktion der Havarie der Costa Concordia“. Diploma Thesis, Bielefeld University.
”
[3] Dankowski, H. (2012). A Fast and Explicit Method for Simulating Flooding
and Sinkage Scenarios of Ships. Phd Thesis, Hamburg University of Technology.
[4] Dankowski, H. and Dilger, H. (2013). Investigation of the Mighty Servant 3
Accident by a Progressive Flooding Method. OMAE 2013.
[5] IMO (2009). SOLAS 2009. International Maritime Organization, Consolidated
Edition. Consolidate Text of the International Convention for Safety of Life at
Sea, 1974, and its Protocol of 1988: Articles, Annexes and Certificates.
[6] IMO (2010). MODU Code. International Maritime Organization. Code for
the Construction and Equipment of Mobile Offshore Drilling Units 2009, 2010
Edition.
[7] Krüger, S. (2013). Personal Communication with Prof. Dr.-Ing. Stefan Krüger
from May to November 2013.
[8] Louagie, M., editor (2003). Designs 03. ShipPax.
[9] MCIB (2013a). Data Meteo LIQO Monte Argentario. Annex 2 to: Report on
the Safety Technical Investigation of Cruise Ship COSTA CONCORDIA.
[10] MCIB (2013b). Report on the Safety Technical Investigation of Cruise Ship
COSTA CONCORDIA. Technical Report, Marine Casualties Investigative
Body.
[11] MCIB (2013c). SIS Comments and MCIB Answers. Appendix 12 to: Report
on the Safety Technical Investigation of Cruise Ship COSTA CONCORDIA.
[12] MCIB (2013d). Stability Dossier. Appendix 10 to: Report on the Safety
Technical Investigation of Cruise Ship COSTA CONCORDIA.
[13] MCIB (2013e). VDR Transcription. Appendix 2 to: Report on the Safety
Technical Investigation of Cruise Ship COSTA CONCORDIA.
[14] MCIB (2013f). Watertight Doors Activity - VDR. Appendix 6 to: Report on
the Safety Technical Investigation of Cruise Ship COSTA CONCORDIA.
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References
[15] Ruponen, P. and Routi, A.-L. (2011). Guidelines and Criteria on Leakage Occurrence Modelling. In FLOODSTAND Project. NAPA Ltd and STX Finland.
[16] Wiggenhagen, M. (2013). Berechnung des Trimmwinkels und der Neigung der
COSTA CONCORDIA aus Havariefotos zum Zeitpunkt des Ankersetzens um
21:48 Uhr. Photogrammetric Expertise, Leibniz University Hannover.
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