Development and application of a numerical wave tank (NWT) for the study of wave interactions
on coastal structures
(Drs J-P Latham, Gerard Gorman and Matt Piggott)
Background The majority of coastal structures such as breakwaters are of rubble mound construction. That
is to say they are typically armoured with massive but loose quarried rock blocks or concrete units (Fig. 1).
Coastal structures are used to reduce and prevent wave damage to harbours and to shorelines but engineers
recognise that current design practice currently suffers from an over-reliance on formulae derived from
laboratory scale model tests. Stability under wave attack relies on the collective behaviour between adjacent
armour units to resist the powerful forces of breaking wave jets and for the wave energy to be converted
into harmless turbulence in the voids between units. The problem has been that current methods cannot
investigate the interdependence of hydraulic and structural stability at the scale of individual units. Even
today, while computational fluid dynamics (CFD) codes are in widespread use by coastal engineers, they
have not been developed with the specific capabilities needed for stability research leading to an
understanding of how these gigantic granular systems work. Numerical methods developed in our AMCG
group http://vgest.net/applications/coastal-engineering/ have the potential to provide such answers but
there are challenges that our team – with the help of a PhD student, hope to overcome.
Xbloc®
Cubipod
Fig. 1. Examples of armour units; Accropode™ on coast protection structure and Core-loc™ units, Azores
breakwater
We
have solved the problem of modelling the loose blocks of the breakwater see Fig. 2a with a powerful
multi-body solids code, Y3D [1]. AMCG has developed a leading fluids code, Fluidity [2] which has generated
excellent breaking waves (see Fig. 2b). Furthermore, coupled Fluidity/Y3D has been applied successfully [3].
Fig. 2. (a) Maximum contact force (Newtons) exerted on each 8m3 unit modelled with Y3D, (b) energetic plunging
wave and splash-up modelled with Fluidity
The Project The preliminary aim of the project is to develop, test and refine the key features required for a
NWT powered by Fluidity designed for coastal wave structure interaction problems. This will include creating
a predefined spectrum of random waves. Simulations using the new NWT with realistic numerical solid
granular structures will be compared with experimental lab and field data and empirical equations. The main
aim is to examine the complex interactions of waves with fixed and loose granular structures.
The Candidate The successful candidate should have a good mathematical background and a good
degree/diploma in an appropriate field such as earth science, physics, mathematics, computer science or
engineering. Good written and spoken communication skills are essential.
1.
Latham J-P, Anastasaki E, Xiang J, 2013, New modelling and analysis methods for concrete armour unit systems using
FEMDEM, Coastal Engineering, Vol:77, 0378-3839, Pages:151-166 | DOI |
2.
Piggott MD, Gorman GJ, Pain CC, et al. 2008: A new computational framework for multi-scale ocean modelling based on
adapting unstructured meshes, International Journal for Numerical Methods in Fluids 56, 1003 – 1015.
3.
Vire A, Xiang J, Milthaler F, et al., 2012, Modelling of fluid-solid interactions using an adaptive mesh fluid model coupled with a
combined finite-discrete element model, Ocean Dynamics, Vol:62, ISSN:1616-7341, Pages:1487-1501 | DOI |
For more information please contact John-Paul Latham (j.p.latham@imperial.ac.uk).
For application details please contact Samantha Symmonds
(E-mail: sam.symmonds@imperial.ac.uk, Tel: +44 (0) 207 594 7339).
(http://www3.imperial.ac.uk/earthscienceandengineering/courses/phdopportunities/phdapplicationprocedure)