Wind tunnel measurements of the resuspension of ideal particles

Resuspension of spherical particles was studied in a small diameter wind tunnel having a smooth resuspension surface. Resuspension was measured at wind velocities from 5 to 22 ms-1 with fully developed turbulent flow in the experimental section of the tunnel. Resuspension rates for 7 μm count median diameter (cmd) particles at 10.5 ms-1 wind velocity were increased by factors of 1.33 and 2.3 when 100 and 200 μm saltation spheres, respectively, were injected upstream of the 7 μm spheres. Resuspension rates for 0.8 μm cmd particles at the same wind velocity increased by factors of 2.5 and 6.7 for injection of equal numbers of 100 and 200 μm spheres, respectively. Vertical flux was determined for the above saltation conditions at a wind velocity of 10.4 +- 0.5 ms-1. Saltation by either 100 or 200 μm particles increased the maximum vertical flux of the 7 μm cmd spheres by less than a factor of 2. Vertical flux of the 0.8 μm cmd spheres was increased by one order of magnitude by saltation with 100 μm spheres, and two orders of magnitude by the same number of 200 μm spheres. (author)