Hydrodynamics and Turbulence Dynamics under Large-Scale Bichromatic Breaking Waves

Experiments were conducted in a large-scale wave flume involving a bichromatic wave group breaking over a fixed barred beach profile. Velocity profiles were measured using optical and acoustics instrumentation at 22 cross-shore locations ranging from the shoaling zone to the inner surf zone. The measurements show that turbulence in the shoaling region is primarily bed-generated and decays almost fully within one wave cycle, in contrast, in the surf zone the breaking-generated turbulence, decays over multiple wave cycles, leading to a gradual increase and decay of Turbulent Kinetic Energy (TKE) during a wave group cycle. The measurements are compared to a two-phase RANS model based on a new stabilized k-ω turbulence closure. The model accurately predicts the water surface elevation, and outperforms standard non-stabilized model in predicting the undertow profile and TKE levels in the shoaling zone and outer surf zone.