VGeST - Virtual Geoscience Simulation Tools

Waves breaking on structures

Two-way Coupling and Wave-Structure Interactions

This research was undertaken in 2012 by Dr.Jiansheng Xiang and Dr Axelle Vire under the supervision of Dr. J-P Latham and Prof. Chris Pain, with assistance from AMCG’s Dr. Gerard Gorman, Dr. Matt Piggott

Coupling of Y3D/Fluidity codes with Interface Tracking. AMCG has developed the immersed body method for solid-fluid coupling.  The forces between the solid and fluid are exchanged on a newly designed supermesh (a mesh comprising the fluid and solid meshes). This allows the forces on the solid and fluid to be equal and opposite and exactly conservative. A major advance has been to combine coupling with interface tracking which allows energetic free surfaces to also be modelled. Below is one of the early results in 2012 showing what is now feasible in the field of coastal engineering. One of the big challenges in understanding breakwater armour stability has been the problem of studying the interdependence of hydraulic stability and structural stability during wave action at full scale.

Several 20 tonne CORE-LOC™ units are positioned on a sloping foreshore with minimum of initial interlocking. Air/water interface tracking methods, using a compressive advective scheme, model the high energy nonlinear wave breaking resulting in wave forces dislodging the units. Mesh adaptivity resolves down and ‘finds’ the solid and is capable of handling complex changing mesh topologies in coupled solid-fluid domains. The colour key shows fluid velocities on the fluid surface and stresses in the solids. The transient tensile stresses, developed during unit impacts with foreshore and neighbouring units, show an ability to model coupled hydraulic and structural stability under wave action and potential concrete vulnerability during bending, torsion and tensile loading modes.

The research shown below, reported in 2009, was undertaken by Dr. Julian Mindel during his PhD studies at Imperial College under the supervision of Dr. J-P Latham and Prof. Chris Pain, with assistance from AMCG’s Dr. Gareth Collins, Dr. Gerard Gorman, Dr. Matt Piggott and Dr.Jiansheng Xiang.

Wave breaking is shown here in a 3D model. Below we apply the model so the wave interacts with a structure.

 


Waves breaking on coastal structures were first modelled by Julian Mindel using ‘Fluidity’ superimposed on solids. The resolution given by mesh refinement between units enables drag forces to be calculated with greater realism. The vertical drag force as the wave breaks over and then acts to uplift the units due to buoyancy forces is shown below.  The simulation utilizes the superimposed mesh two-phase method (see fluid-solid interaction) and was run on one processor.

Velocity profiles for one moment just after wave impact are shown in the figure below.

It is also possible to deposit packs of armour units using DEM methods to create granular packs through which wave action can be studied.

The two-way coupling has been validated and an example of coupled DEM/Fluids modelling was shown, see colliding spheres fluid-solid interaction simulation.

Reference

Dr. Julian Mindel PhD Thesis