Aerodynamics of a portable wind erosion tunnel for measuring soil erodibility by wind

Abstract

Portable wind erosion tunnels must satisfy several aerodynamic criteria to ensure that the flow within them acceptably reproduces the atmospheric flow causing natural wind erosion. We define these criteria and use them to assess the flow and turbulence in two alternative designs of portable wind erosion tunnel: the first has a working section with an approximately triangular, 'tent-shaped' cross section, while the second has a conventional, rectangular working section. The measurements were made with Pitot-static tubes and X-configuration hot-wire anemometers, over stable (non-eroding) rough surfaces, mainly mowed grass of height 1 cm. We found that, with careful attention to flow conditioning elements such as honeycombs and tripping fences, an acceptable flow can be achieved in the rectangular tunnel. The flow in the tent-shaped tunnel is less satisfactory, exhibiting departures from the logarithmic wind profile law which depend on the surface roughness.