Turbulence production by nonbreaking waves: Laboratory and numerical simulations

This paper investigates the effect of wave motion on the turbulence in close proximity to the surface. Some existing theories suggest mechanisms by which the energy is transferred from waves to turbulence. However, scarce empirical results struggle to establish the existence of such energy transfer and are not sufficient for thorough validation of existing theories. The present investigation relies on both experimental and numerical approaches. Turbulent velocities at the water surface were measured in a laboratory wave tank with high precision using the thermal‐marking velocimetry technique. Numerically, a fully nonlinear model for the wave motion was coupled with Large Eddy Simulation for the turbulent motion. The results confirm the turbulence production due to wave motion. The turbulent kinetic energy was found to be a function of time, wave steepness, wave phase, and initial turbulent conditions. Additionally, turbulent motion near the surface was found to be horizontally anisotropic due to the formation of near‐surface eddies, elongated in the direction of wave propagation. Key Points Nonbreaking surface waves were found to generate near‐surface turbulence Wave‐induced turbulence was found to intensify near crests of steeper waves Initial turbulence controls the wave‐induced turbulence production