Turbulence Simulation of Laboratory Wind-Wave Interaction in High Winds and Upscaling to Ocean Conditions
Technical Report,01 Nov 2011,30 Sep 2016
University of New South Wales SYDNEY Australia
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Our LES modeling study of waves strongly forced by winds investigated air-sea fluxes characterized by strong air flow separation over a very steep wave field. For propagating steep wave forms with fixed shape, the dominant effect on momentum flux was geometrical steepness not the fluid speed distribution along the boundary. Adding a realistic surface wind drift current produced only a small increase in the mean wind profile, and a minor reduction in the form drag fraction. We investigated passive scalar fluxes and found that the momentum and scalar fluxes differ fundamentally in their dependence on surface properties and flow separation. Strongly-forced wind seas are characterized by group modulation. Using compact steep chirped wave packets, we investigated the influence of strong temporal and spatial modulation, which introduce separation events contributing large local wave form drag spikes that add significantly to the mean stress. Finally, we investigated upscaling these results to strongly forced ocean conditions with a much wider wave spectral bandwidth. Overall, the fundamental aerodynamic behavior discovered in our LES study has a strong counterpart for short steep waves in the spectral tail.
- Physical and Dynamic Oceanography