Direct numerical simulations of coupled turbulent wind-wave flow at high wind speed

The interaction between wind currents and ocean waves at wind speed above 25 m/s remains poorly understood. To address this research gap, we investigate a two-phase boundary layer at high wind speed fully resolving the evolving wave field using direct numerical simulations of the Navier-Stokes equations, combined with a geometric Volume-of-Fluid method, to capture the gas-liquid interface. The simulations utilize Basilisk's adaptive mesh refinement framework, ensuring sufficient resolution at the two-phase interface. In our study, we vary the ratio between wave speed and friction velocity c/u_s = [1,2] and the initial wave steepness a₀k=[0.2-0.3], while keeping the friction and wave Reynolds numbers and the Bond number equal to Re_τ=720, Re_w=25000 and Bo=200. Upon an initial transient, the water waves undergo a cycle of growth and breaking stages. For each case, we quantify the stress and energy budget partition between pressure and viscous stress contributions at the interface. We systematically evaluate how the velocity and pressure profiles change in both phases during pre- and post-breaking events. Finally, by increasing the Bond number to Bo=1000, we assess how a significant amount of sea spray affects the exchanged momentum and energy fluxes.