Research On The Volume Fraction Of Sand Particles In The Sand Bed In The Wind Field

The wind-blown sand movement is a typical gas-solid two-phase flow. There is interaction between the wind and the sand particles on the wind-blown loose sand bed. Hence brings self-organization behaviors to the sand particles on sand bed, which causes changes of volume fraction of sand particles in the sand bed and show the differential of the different locations in sand bed. However, it is difficult to obtain the actual volume fraction of sand of the different locations by the experiment. In order to prevent the volume fraction of sand beyond its physical limits, we have to assume the maximum volume fraction of sand particles in the numerical simulation. That means, the maximum volume fraction of sand particles and the volume fraction of sand particles in the sand bed appears to be the key element in the simulation of gas-solid two-phase flow, which can’t be ignored when studying the dynamic mechanism of the sand bed erosion, or the transportation and deposition of eroded sand bed. Therefore, this paper used Euler-Euler two-fluid model in the FLUENT software, and studied the effects of the maximum volume fraction of sand particles on windblown sand cloud and the effects of the wind field on the volume fraction of sand particles in the sand bed.First of all, based on the Eulerian-Eulerian two-fluid model, and simulated of wind tunnel experiments, comparison of results between numerical simulation and field observation, the results show that, the simulation results of Euler two-fluid model are reliable.Secondly, based on the Eulerian-Eulerian two-fluid model and simulated the development of the wind-blown sand bed in two-dimensional space, the effects of the maximum volume fraction of sand particles on windblown sand cloud are discussed. The results show that, with the increase of the maximum volume fraction of sand particles, the wind velocity and velocity of sand particles rise significantly in the saltation layer, while the volume fraction of sand particles in the windblown sand cloud decreases within certain height above the surface of sand bed, but once it goes higher than this height value, the influence of the maximum volume fraction of sand particles on the volume fraction of sand particles in the windblown sand cloud can be nearly ignored.Finally, based on the Eulerian-Eulerian two-fluid model, the effects of the inlet velocity and turbulence intensity on the volume fraction of sand particles in the sand bed are discussed. The results show that, because of the wind-blown sand movement, the volume fraction of sand particles in the sand bed presents ripples regularity at the same height of the sand bed. From the ground to the surface of the sand bed, the average volume fraction of sand particles in the sand bed gradually decreases. The influence of the wind velocity on the volume fraction of sand particles in the sand bed can be nearly ignored within certain height above the ground, but once it goes higher than this height value, along with the increase of the wind velocity, the average volume fraction of sand particles in the sand bed decreases. Similarly, within the depth of the sand bed is interference by airflow, with the increase of the inlet turbulence intensity increases, the average volume fraction of sand particles in the sand bed decreases.