On Conditions for the Wind Removal of Soil Particles

Studied the moving of airflow around spherical sand particles of diameter 200 μm in solving the problem of the wind removal of soil particles. Used their a regular arrangement on a plane at distances close to or smaller than their diameter with gaps of 50–250, 300, and 700 μm at velocities of 2‒3.1 m/s. The problem is solved using the OpenFOAM open software package. A multilevel mesh adapted to the shape of microrelief elements and smoothing the area of the contact of spherical particles with the lower plane by cylindrical shapes of small radius is applied. The k -type of irregularities with large distances (above 300 µm) is used in calculations of the wind removal of particles. The proximity of the surface resistance values for 50- and 300–700-μm gaps between particles indicates the importance of taking into account the air motion in medium pores (inside a densely packed undersurface layer). The average distances between particles are estimated by analyzing the sand porosity data. It is shown that they correspond to the case of d -type surface irregularities, when the processes in the layer between particles are significant. At distances of 100–250 μm, the region between particles is characterized by the presence of recirculation zones, which determines an order of magnitude greater surface resistance. The dynamic friction velocity is maximum for 200 μm and minimum for 100 μm. The velocity becomes close to the critical value with changes the distance between particles, at which, according to experimental data, a particle of this size can escape from the surface. Values of the viscous surface layer height, which is related to the roughness parameter, agree well with the empirical data for different distances between particles. The buoyancy force acting on the surface particles and calculated proceeding from estimates for the difference of the pressure on the opposite sides of the particles is maximum for the distances of 200 μm between the particle surfaces, minimum for 50 and 100 μm, and gives an inverse pressure against the surface for 150 and 250 μm.