Relationship between surface slope, average facet size, and facet flatness tolerance of a wind-disturbed water surface

Abstract

Experimental relationships are given relating wind velocity to the parameters given in the title. Photographically obtained profiles of waves in a short-fetch water-wind tunnel were used as the source of data. The term ‘roughness factor’ is defined as the ratio of facet flatness tolerance to facet length. Average roughness factor increases with wind velocity in the region of near-zero facet slope. For facet slopes greater than about +10° and −10°, the situation is reversed. In this region, the average roughness factor is greater for positive slopes than for negative slopes.