A two layer model is developed to investigate the movement of a single round particle. The reference layer is set as a slope with the repose angle 30°, and is covered regularly with round particles with the same diameter. The free layer in which the same diameter can move freely is just on the reference layer. A periodic rolleject- collide movement is found, and the frequency is 0.39 g/D , which is independent of the initial velocity and close to the velocity gradient. The constant projection angle is 51.2° and the spin angular velocity is 16 r/min. This self-hold of frequency determines the sands in the free layer to move forwards integrally, and may be the basic acoustic mechanism of the booming sands.

The turbulent flow near the windbreak is simulated in the boundary layer wind tunnel. Wavelet analysis is used to study the turbulent signal in the lee side of the windbreak. Compared with the flow without windbreak, the turbulent energy and the frequency of vortex are reduced dramatically. The evidence shows how the wind break prevents the dust emission.