Large eddy simulation of three-dimensional vortex structures in cnoidal waves over a submerged step

A three-dimensional (3D) numerical wave tank based on Large Eddy Simulations (LES) is employed to study the interaction of a submerged rectangular step with periodic waves in shallow water depths, with a good agreement with experimental measurements. The effect of step height is studied in terms of wave elevations, vorticity eld and 3D vortical structures. The shallow and intermediate cases have limited effect on the water surface fluctuations both upstream and downstream from the structure whereas a dominant wave structure interaction is observed in the steep case resulting in wave breaking downstream from the step. The effect of step height variation on 3D vortical structures is also investigated in detail and results suggest that three dimensionality is almost negligible in the shallower step whereas in the remaining cases, dominant 3D effects are formed generating discontinuities in the primary spanwise eddies and forming small billows with zero spanwise vorticity interacting with the floor bed, the structure and the water surface.