CALCULATION & SELECTION OF BOW THRUSTER
1. Wind Resistance
The wind resistance can be calculated by this following formula:
RA : Ka x Aa x Va2
Where:
Ka : Wind's coefficient
=
Aa : Projected area of ship above the waterline
Va : Wind's relative speed to the ship movement
=
=
So, the result of wind resistance's calculation is:
RA : 0,735 x 643,76 x 102
:
68135.5584 N
:
68.1355584 kN
2. Frictional Resistance
The frictional resistance can be calculated by this following formula:
RW : Kw x Aw x (( Vw + Vs )2 + 0,33 x ( Vw + Vs ))
Where:
Kw : Coefficient of frictional resistance
=
Aw : Wet Surface Area ( WSA )
Vw : Wave's speed
Vs : Ship's speed at operation of bow thruster
=
=
=
So, the result of frictional resistance's calculation is:
RW : 1,212 x 2802,997 x (( 1,03 + 0,514 )2 + 0,33 x ( 1,03 + 0,514 ))
: 23752.089796 N
: 23.752089796 kN
3. Form Resistance
The form resistance can be calculated by this following formula:
RV : Kv x As x Vs2
Where:
Kv : Form's Coefficient
=
As : Projected area of ship under the waterline
Vs : Ship's speed at operation of bow thruster
=
=
So, the result of form resistance's calculation is:
RV : 73,2 x 233,153 x 0,514
:
4439.074576 N
:
4.439074576 kN
4. Resistance Caused by Equipments
The resistance caused by equipments can be calculated by this following formula:
RP : Kp x Ds2 x ( Vw + Vs )2
Where:
Kp
Ds
Vw
Vs
:
:
:
:
Coefficient of resistance caused by equipments
Tunnel thruster's diameter
Wave's speed
Ship's speed at operation of bow thruster
=
=
=
To define the thruster's diameter, have to know the specification of bow thruster. Therefore, calculating the initial power of bow
thruster with using the graphic of lateral thruster.
From the graphic above, it can be conclude that:
f :
0.078 kN/m2
So, the value of initial power is:
Yo : f x Lpp x T
: 0,078 x 72 x 4,24
:
23.8 kN
Po : Yo / Co
: 23,8 / 0,15
:
158.75 kW
:
212.88 HP
With the requirement specification above, select the bow thruster:
Merk : Tunnel Thruster
Type : Hydraulic Pod Motor Driven
Power : 200 - 250
HP
Tunnel Diameter :
36 inch
:
914.4 mm
:
0.9144 m
So, the value of resistance caused by equipments is:
RP :
52.35 N
:
0.05235 kN
5. Total Resistance
So, the value of total resistance is :
RT : RA + RW + RV + RP
:
96.38 kN
CALCULATION OF BOW THRUSTER MANOEUVERING
1. Define the Value of Thrust Power ( f )
The value of thrust power ( f ) is can be calculated by following formula:
f : Yo / ( Lpp x T )
[N/m2]
Where:
Yo : Effective force
T : Draught of ship
Lpp : Length of perpendicular
So, the value of thrust power is:
f :
=
=
=
70.2 N/m2
2. Define the Value of Angular Velocity ( ѱ )
The value of angular velocity ( f ) is can be calculated by following formula:
ѱ : (k/Lpp) x (f/p)0,5
[o/s]
Where:
k : Degree
=
f : Thrust power
Lpp : Length of perpendicular
p : Density
So, the value of angular velocity is:
ѱ :
=
=
=
0.62 o/s
From the calculation above, it means that to make one full rotation (360 o), time's needed is 580,645 seconds or 9,677
minutes.
From the calculation above, it means that to make one full rotation (360 o), time's needed is 580,645 seconds or 9,677
minutes.
CALCULATION OF BOW THRUSTER MANOEUVERING
1. Define the Value of Thrust Power ( f )
The value of thrust power ( f ) is can be calculated by following formula:
f : Yo / ( Lpp x T )
[N/m2]
Where:
Yo : Effective force
T : Draught of ship
Lpp : Length of perpendicular
So, the value of thrust power is:
f :
=
=
=
78 N/m2
2. Define the Value of Angular Velocity ( ѱ )
The value of angular velocity ( f ) is can be calculated by following formula:
[o/s]
ѱ : (k/Lpp) x (f/p)0,5
Where:
k : Degree
=
f : Thrust power
Lpp : Length of perpendicular
p : Density
So, the value of angular velocity is:
ѱ :
=
=
=
0.78 o/s
From the calculation above, it means that to make one full rotation (360 o), time's needed is 679,2453 seconds or 11,3
minutes.
USTER
0.735 kgm/m4
643.76 m2
12 m/s
1.212 kgm/m4
2802.997 m2
1.03 m/s
0.51 m/s
73.2 kgm/m4
233.153 m2
0.51 m/s
26.4 kgm/m4
1.03 m/s
0.51 m/s
e, calculating the initial power of bow
VERING
23811.84 N
4.24 m
80 m
190 o
70.2 N/m2
80 m
1025 kg/m3
's needed is 580,645 seconds or 9,677
VERING
23811.84 N
4.24 m
72 m
190 o
90 N/m2
72 m
1025 kg/m3
s needed is 679,2453 seconds or 11,32
2.76
643.494