LAUSR

Abstract A series of wind tunnel experiments was carried out using isolated, surface-mounted elements of varied idealized geometric form to evaluate the relative efficacy of these in wind erosion control. The topography of the bed surface was scanned in high resolution, before and after each wind erosion event, giving the net volume change. The perturbed airflow structure was sampled via laser Doppler anemometry. The volume of erosion initiated by the flow perturbation relative to that of the roughness element was greatest for a rectangular prism in either orientation (face-on 2.5; edge-on 4.0), minimal for a hemisphere (0.2), and below detection for a reference (streamlined) form. Roughness elements that trigger strong downwelling in the perturbed flow and vortex impingement on the bed surface appear to initiate particle motion. Consequently, they are less desirable for wind erosion control, even though they usually have large form drag and demonstrate substantial kinetic energy (KE) dissipation in the wake flow. Hemispheres, with generalized upwelling along both the windward and leeward faces and strong turbulent KE dissipation associated with flow separation along the sidewalls, may present an optimal solution with minimal bed scour.