Computation and Theoretical Studies of Surface Water Wave Effects on Turbulence

The interaction of turbulence in the lower marine atmospheric boundary layer and the upper ocean with waves at ocean surfaces is a profound problem in fluid mechanics. On the air side, the convex and concave wavy water surface poses constraints on the wind turbulence and the wave velocity directly distorts the near-surface air flow. Observed at scales larger than the waves, the wind field can be treated as a turbulent boundary layer over a rough surface. However, much more complex than the stationary rough walls in engineering applications, the roughness elements at sea surfaces (i.e., different wave components) are all in motion, and the waveforms of different sizes propagate at different speeds according to the wave dispersion relationship. On the water side, the orbital velocity of the wave generates a periodically-alternating strain rate field that distorts the turbulence. Meanwhile, the wave produces mass transport (i.e., Stokes drift) in the wave propagation direction, which leads to a mean shear from the viewpoint of Lagrangian average. The strain rate associated with the Stokes drift velocity is typically an order of magnitude smaller than the instantaneous strain rate associated with the wave orbital velocity, yet the cumulative effect of the former can be significant. Due to the importance of applications and the limited understanding of the fundamental mechanisms of turbulence-wave interaction, there is a critical need to advance the theory and develop accurate and efficient modeling capabilities applicable to various engineering and environmental problems. In this talk, some recent advancements in high-fidelity simulations and theoretical modeling and analyses will be presented.