Abstract:

The two-phase flow motion of wind and sand on the gravelly gobi surface during dust storms has been a subject of much interest in wind and sand physics. However， due to technical limitations， field observations and wind tunnel experiments are difficult to capture large-scale particle motions. To this end， this paper analyzes the wind-sand two-phase flow motion during the incoming dust storm under different gravel cover by constructing a three-dimensional field numerical simulation of fluid-particle collisional mutual feedthrough model. It is found that the modified solution based on the 3D field fluid-particle collisional mutual feedthrough model can simulate the wind-sand two-phase flow motion on the gobi surface more accurately. The simulation results further show that： （1） The wind-phase velocity decreases with the increase of gravel cover for different incoming dust storm processes， and forms a Bagnold focus near the surface of the gobi where the gravel cover is greater than 40%. Compared with the wind phase， the velocity decrease in the sand phase is not obvious. In addition， above 4 cm from the gravel bed surface， the velocities of both wind and sand phases remain basically the same. （2） When the dust storm velocity is greater than 10 m·s^-1， the intersection of the two phases of wind and sand flow velocity is formed in the height range of 1.5-2.1 m from the ground， and the phenomenon of “ Wind is faster than sand ” and “ Sand is faster than wind ” is manifested above and below the intersection. （3） During the dust storm process， the near-surface dust concentration shows a “pulsation ” law along the mean line， which is manifested as the cycle of surface dust deposition and re-release. At the same time， the gravel coverage will directly affect the distribution of dust deposition. When the coverage is greater than 40%， it can effectively suppress dust release.

Key words: gobi, gravel cover, numerical simulation, wind and sand two-phase flow motion, velocity intersection