Wind flow characteristics over rough surfaces
The aim of this research is to study wind profile characteristics as they are modified by an artificially roughened erodible surface for a range of roughness densities. Surface roughness acts to protect the surface from wind erosion, principally by absorbing some of the momentum so that the wind shear stress is partitioned between the roughness elements and the intervening surface. A series of wind profile experiments were conducted at the Jornada Experimental Range, USDA, ARS, in Las Cruces, New Mexico, where changes in wind profile parameters were evaluated for a staggered roughness configuration comprising of 1,920 5-gallon buckets. The buckets were used to produce four different roughness densities in order to study changes in wind flow patterns and momentum over the roughness configurations. The results indicate that the controlled modification of surface roughness is essential in understanding processes already complicated by such factors as irregular patterns, variability in wind speed, and wind direction. The systematic decrease in element density on the bare surface has demonstrated the ability of roughness elements to extract momentum from the flow. In addition, the present methods for estimating surface roughness reveals that they are only capable of describing a uniform array of elements; therefore, a roughness descriptor needs to be devised in order to address the issue of non-uniform arrays of elements.