The two-phase flow theory about dust storm's vertical transport, part Ⅱ: The air column entrainment model

To improve the air particle method in the previous paper, the air column entrainment method is used to study dust storm sedimentation. In the method, entrainment between the column and the environment is included, as is the turbulent exchange within the column. In a homogeneous environment, the computational results suggest that favorable conditions for sedimentation are larger initial dust concentration disturbances and smaller initial temperature disturbances; and furthermore, the larger the diffusion coefficient of temperature, the quicker the dust sedimentation, but the larger the diffusion coefficient of dust concentration, the slower the dust sedimentation. The turbulent process has little influence on the sedimentation. We further consider some more real environment conditions with vertical dust concentration and temperature gradients, the results suggest the same favorable conditions for the sedimentation in the above homogeneous environment. And meanwhile, four processes which are not conducive to the sedimentation are given: (1) ascending concentration variation process; (2) descending concentration variation process; (3) ascending temperature variation process; (4) descending temperature variation process. On the basis of the definitions of these processes, we can study the impacts of parameters on the sedimentation, and results show that the temperature diffusion is conducive to the sedimentation; and the dust concentration diffusion is not conducive to the sedimentation; the larger vertical temperature turbulent exchange coefficient is more conducive to ascending in the slowly sedimentation region, even in the non-sedimentation region; and the larger vertical dust concentration turbulent exchange coefficient is more conducive to the sedimentation.