Momentum Transfer at the Air-Water Interface

Abstract

Wind action over water generates waves and surface drift. The logarithmic velocity profile in air can be used to determine the surface stress with a suitable choice of roughness height. A corresponding logarithmic profile is found below the interface and yields a surface stress equivalent to that found from the air profile. The wind induced set-up depends on water depth, surface and bottom boundary stresses, and atmospheric pressure gradient. Modelling relationships to simulate set-up under laboratory conditions are discussed. The momentum transfer from wind to waves is found to be approximately 10–20 percent of the total wind induced stress. The net energy transfer to any wave spectral component depends on nonlinear wave-wave transfers in addition to that received directly from wind less that dissipated by viscosity or turbulence.