Effects of Shoaling Surface Waves on Wind Turbulence and Air-Sea Momentum Exchange

In order to effectively model near-shore physics, for example in storm surge models or in engineering models for off-shore wind, it is important to understand the efficiency with which momentum is transferred between the wind and the ocean in shallow coastal waters. However, while there is observational evidence that shoaling waves may increase the drag coefficient, the impact of shoaling wave shapes on the drag coefficient is not well understood. Thus, large eddy simulations (LES) are conducted to examine the extent to which shoaling, wind-forced waves modify the drag coefficient and the wind turbulence field above them, including the degree and frequency of flow separation, the pressure form drag, and the mean wind profile. The LES is run with different combinations of wind forcing and shoaling wave shape in alignment with the observational wave tank data obtained using the Particle Image Velocimetry (PIV). The test cases span breaking and non-breaking waves, and a deep-water case is also included for the sake of comparison.