CFD modelling of surface wave breaking in a long channel

Modelling wave breaking at relatively large Reynolds numbers remain a challenge for both numerical modeler and experimentalists, due to the complexity between the two-phase air-water interactions, highly turbulent unpredictable hydrodynamics, and a lack of solid validation datasets. This study presents a recent attempt to simulate a three-dimensional breaking wave propagating in a long rectangular channel, at relatively high Froude (Fr1 = 1.5) and Reynolds number (Re ~ 10^5). The numerical model used a Large Eddy Simulation coupled with a Volume of Fluid method to track the interface between air and water. The turbulence was injected using a Synthetic Eddy Method. The numerical results were validated against experimental datasets, which were collected under the exact same initial and boundary flow conditions in a controlled laboratory environment. Systematic validations showed: (1) the generation process of a breaking shock wave is a complicated process which was not accurately modelled by simple boundary conditions; (2) the propagation process following an unrealistic generation could lead to false prediction in free-surface profile, velocity field, and turbulent mixing; (3) the bubble motions (collision, agglomeration and break-up) during surge propagation were poorly predicted, comparing to observations of real-fluid flow; (4) the de-aeration process was grossly underestimated in the numerical result.