Wind tunnel evaluation of a wedge-shaped aeolian sediment trap

A detailed set of tests in a wind tunnel investigated the characteristics of flow and sampling efficiency of a low cost sediment trap that can be used in wind tunnels and field applications. The trap is constructed of thin sheet aluminum and has a wedge shape (32 degrees internal inlet angle with a 20 x 500 mm rectangular inlet orifice that extends 40 mm beyond the wedge form. Relatively unimpeded airflow through the trap is achieved by the large exit area (130 x 500 mm) which is covered with fine, stainless steel mesh (62.5 mu m openings, 60% porosity), and collected all but the finer (silt) sediment sizes. Despite its angular shape, the trap has good characteristics of flow and a very high sampling efficiency (> 90%) over a wide range of wind velocities because of its near isokinetic characteristics of flow. Results also indicate that this trap, and others that have wide side profiles, are very sensitive to incident wind angle. Incident angles > 5 degrees significantly reduce the sampling efficiency and promote scour around the trap inlet.