Analysis Of Mechanism For Snow Drift Above A Flat Particle Bed

According to the adhesion degree of snow grains on the bed, this paper have established different initiation models and respectively analyzed the relationship between threshold wind velocity and particle size, temperature and snow cover time at the temperature range of - 30℃- 0℃. The results show that when other factors do not change, the critical threshold wind velocity will increase with the particle size of snow grains, the critical threshold wind velocity increase with time of snow cover, and reach a steady value finally; when the temperature below zero, the critical threshold wind velocity will increase with the temperature of snow surface.Established a movement model of single snow particle and discussed the influence of various factors on motion trajectory of snow particle at different situations. The results show that besides the gravity and the drag force, the saffman force, the magnus force, the electric field force as well as motion randomicity also have important influence to a snow grain movement, which changes with different wind speed, particle size and particle density.Based on the analysis of threshold and movement mechanism of a snow particle, a computation model of the evolution process of wind-snow drift has been established, combined with initial velocity distribution function we analyze the structure of the snow drift and compare it with the value of cold wind tunnel test. The result demonstrated that after the wind blow snow develops to a stable state, the movement of snow grains has the obviously effects on the wind field; snow grain number's density and the horizontal quality flux obey the negative exponent distribution with height, and the computed results will be closer to the actual when the effects of Saffman force Magnus force and electric field force are taken into consideration. Furthermore the motion randomicity of mobile particle has obvious effects on the computed results too. On the basis of splash function, we simulated the evolution of snow drift and calculated the time for the entire system to reach a steady state of snow drift at several wind speeds. Compared to the experimental results of snow flux in steady state, it suggests that the simulating results are good accordance with the experimental results.