LAUSR

In this letter, the concentration of particles with size less than 10 μm (PM10) and flow velocities are measured synchronously at different heights in a sand storm, a high-Reynolds number multi-phase turbulent boundary layer. It is revealed that the low-speed very large scale motions (VLSMs) are recurrent with a frequency dominating the streamwise velocity power spectra and modulate the streamwise distribution of PM10 concentration. In the logarithmic layer, the low-speed VLSMs correspond to weak shear stress on the bottom surface and hence decrease the PM10 upward flux. In the higher region, the high-speed VLSMs enhance both the streamwise and the upward transportation of PM10 because of the positive correlation between the velocity and the particle concentration perturbations.