Numerical Investigation of Interactions between Surface Waves and Upper-Ocean Turbulence
Anqing Xuan1,2, Bingqing Deng2,3 and Lian Shen1,2, (1)University of Minnesota, Department of Mechanical Engineering, Minneapolis, MN, United States, (2)University of Minnesota, St. Anthony Falls Laboratory, Minneapolis, MN, United States, (3)University of Minnesota, Saint Anthony Falls Laboratory, Minneapolis, MN, United States
Abstract:
Numerical simulations are performed to investigate the interaction between surface waves and turbulence in upper oceans. In our simulations, the wave motions are directly resolved to include both the phase-averaged Stokes drift and instantaneous distortion effect of surface waves on the turbulence beneath. A parallel hybrid spectral/finite-difference, with pseudo-spectral discretization in the horizontal plane and second-order finite-difference discretization on staggered grid in the vertical direction, is adopted. Fully nonlinear kinematic and dynamic free-surface boundary conditions are employed on the surface. The influence of surfaces waves on turbulence is successfully revealed in our simulations. In the cases of wind-driven shear turbulence interacting with waves, Langmuir circulations are clearly present in the simulations, and are found to be intensified as the turbulent Langmuir number, the root square of the ratio of the friction velocity to the surface Stokes drift velocity Lat=(u*/US)1/2, decreases. Our simulation results also indicate that the presence of Langmuir cells substantially changes the mixing processes in the upper ocean.
