LES and RANS Simulations of Wave Breaking Over a Submerged Horizontal Plate

Wave breaking is a complex phenomenon which typically involves strong air entrainment which in turn affects the flow field. When taking place at the shoreline, the wave breaking may cause severe erosion and beach deformation.

Wave breakers may be considered to force offshore breaking. It was shown in several earlier studies that a submerged horizontal plate may serve as such wave breaker. Waves propagating over the plate are transformed to shallow water waves and breaking takes place over the plate.

Vortex generation and shedding around a plate was analysed by means of simple 2D simulations and low-resolution PIV (Particle Image Velocimetry) in Bung et al. (2008). In the present paper, more sophisticated methods will be applied to obtain deeper insight in the vortex formation and the energy dissipation around the structure.

Numerical modelling will be conducted by both, full 3D LES and RANS (with RNG k-eturbulence closure) simulations using the commercial software FLOW-3D. The performance of both methods will be compared to each other and to laboratory data. Instead of the PIV method, Optical Flow and surface detection methods will be employed in the physical model, as implemented in the Flow-CV toolbox (Bung & Valero 2017), using high-speed recordings with HD resolution. The advantage of Optical Flow is the much higher density of velocity data compared to PIV (yielding velocity information at every image pixel).

The paper will provide a better understanding on the flow processes in this complex type of flow with air-water-fluid-interaction as well as an evaluation of different numerical simulation methods.

References

Bung, D.B.; Hildebrandt, A.; Oertel, M.; Schlenkhoff, A.; Schlurmann, T. (2008): Bore propagation over a submerged horizontal plate by physical and numerical simulation, 31st International Conference on Coastal Engineering (ICCE), Hamburg.

Bung, D.B.; Valero, D. (2017): FlowCV - An open-source toolbox for computer vision applications in turbulent flows, 37th IAHR World Congress, Kuala Lumpur.