Wind velocity distribution over wind-generated water waves

Abstract

The results of laboratory investigations conducted to study the wind dynamics above wind-generated water waves are presented in this paper. Available field measurements strongly suggest a logarithmic law for the wind-velocity distribution in the region close to the perturbed water surface. The present study provides adequate quantitative evidence to conclude that the wind-velocity distribution over wind-generated water waves in the laboratory is also logarithmic and is well represented by the “inner law of the wall”. For high wind velocities the air flow over the water surface corresponds very well with the turbulent flow over a fully rough boundary, the roughness heights being of the same order of magnitude as the wave heights. The data at low free stream velocities seems to support Csanady's concept of a supersmooth surface. Charnock's empirical relationship established on the basis of field measurements is found to be valid at high wind velocities, indicating good correlation between the laboratory results and field observations. Coupled with the earlier finding that the statistics of wave heights and the energy spectra are reproduced well, these studies highlight the versatility of wind water-wave flumes as useful experimental tools.