Wind tunnel measurements of the resuspension of ideal particles

Abstract 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 m s −1 with fully developed turbulent flow in the experimental section of the tunnel. A long inlet ( L / D of 36) provided a thick boundary layer in simulation of the atmospheric boundary layer. Resuspension rates and vertical flux were determined for monolayers of σ g = 1.6) particles at 10.5 m s −1 wind velocity were increased by factors of 1.33 and 2.3 when 100 and 200μm saltation spheres, respectively, were injected upstream of the 7μm spheres. Resuspension rates for 0.8μm cmd ( σ g = 2.4) particles at the same wind velocity increased by factors of 2.5 and 6.7 for injection of equal numbers of 100 and 200μm spheres, respectively. Resuspension rates (Λ) of the 7 μm cmd spheres as a function of velocity (U) from 7 to 20m s −1 were Λ = 3.2 × 10 −3 U −3 for no saltation particles and Λ = 5.7 × 10 −2 U 1.8 and 1.6 × 10 −3 U 2.1 for saltation with equal masses of 100 and 200μm saltation spheres. Vertical flux (particles cm −2 s −1 was determined for the above saltation conditions at a wind velocity of 10.4 ± 0.5 m s −1 . Saltation by either 100 or 200μm particles increased the maximum vertical flux of the 7μm cmd spheres by less than a factor of 2. Vertical flux of the 0.8μm cmd spheres was increased by one order of magnitude by saltation with 100μm spheres, and two orders of magnitude by the same number of 200μm spheres.