VGeST - Virtual Geoscience Simulation Tools

Wave modelling

News: July 2012. Preliminary work has begun on the development of a Numerical Wave Flume powered by Fluidity. These results were presented in a paper by Johannes Spinneken:

Spinneken J , Heller V , Kramer S , Piggott M , Viré A, Assessment of an advanced finite element tool for the simulation of fully-nonlinear gravity water waves (accepted), 22nd International Ocean and Polar Engineering Conference ISOPE, 2012, see: Spinneken et al 2012 ISOPE Conference

The earliest work by AMCG on wave modelling 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.

The code capabilities can be compared with the popular benchmark experiment of a collapsing water column with obstruction.  The figure shows the experiment on the left with the equivalent stage of the simulation in blue on the right, note how closely the violent flows are captured.

Multi-fluid (air and water) interface modelling on 3D unstructured finite element meshes has been achieved using a compressive advection scheme to ensure interface sharpness to the limit of the local resolution. This is of particular interest when modelling breaking waves. A functional-based mesh enhancement by movement (Arbitrary Lagrangian Eulerian) method was implemented to improve efficiency, aid interface sharpness achieved by the compressive scheme, and exploit Lagrangian benefits (Mindel et al. 2007). Surging, plunging, spilling waves have been created using different smooth foreshore slope angles, the videos below show plunging and spilling waves resolved by mesh adaptivity.

Plunging waves Spilling waves

 

The plunging simulation shows the violent plunging tongue and air-water mixing with bubbles eventually surfacing. This level of detail is achievable because of the adaptive mesh technology which can be seen to refine where the greater resolutions are required. This work was presented by Mindel at the 5th Coastal Structures Conference, Venice 2007. Two close-up snapshots of the wave breaking simulation are shown below.

Validation study (MARIN/Kleefsman data set)

The classic experimental validation data set for the challenging CFD problem of a 3D domain with a collasing water column producing a wave striking a vertical rectangular block obtained in the MARIN experimental facility was reported by Kleefsman.  Recent 3D simulation of the six-second experiment by Mindel produced the pressure sensor results shown below, which are within 10% of the experimentally determined peak pressure transient of the observed sensor readings (smoother line of graph is sensor).

References

Dr Julian Mindel PhD Thesis 2009

Mindel, J.E., Collins, G.S., Latham, J.-P., Pain C.C. and Munjiza, A. 2007. Towards a numerical wave simulator using the two-fluid interface tracking approach combined with a novel ALE scheme. Proceedings of the Fifth International Conference on Coastal Structures, Venice, Italy, July 2-4, 2007. Published by World Scientific Publishing Co. Pte. Ltd. 2009, 1465-1476.