The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Langmuir turbulence, resulting from the nonlinear interaction between surface gravity waves and wind-driven shear currents, significantly contributes to ocean mixing and the air-sea exchange of mass, momentum, and heat. Previous studies of Langmuir turbulence are often based on wave-phase averaged large eddy simulations (LES), or more recently wave-phase resolved LES or direct numerical simulations (DNS). In both cases a surface wind stress is prescribed and the air-sea exchange of momentum is not directly resolved. To resolve such air-sea exchange of momentum and study its role in the generation and evolution of Langmuir turbulence using a two-phase flow DNS, we first examine the interaction between surface gravity waves and wind-driven shear currents in such simulations and benchmark against previous wave-phase resolved simulations. Initial results show characteristic structures of Langmuir cells, including pairs of counter-rotating vortices and elongated streamwise streaks. By decomposing the flow velocity into mean current, wave orbital motion, and turbulence fluctuation, the impact of wave-induced phase-dependent strain on the underlying turbulence and the enhancement of streamwise vorticity is analyzed.

Langmuir turbulence, wave-current interactions, surface gravity waves