SPH Numerical Study On The Movement Characteristics Of Sand Flow

The movement of wind-sand flow is a self-organized,multi-scale,complex,and nonlinear gas-solid two-phase flow movement.Different surface morphologies have different effects on the movement characteristics of sand particles and the characteristics of the gas flow field.Based on the SPH method,this paper uses numerical calculation methods to analyze the movement characteristics of the sand flow under different sand beds from the micro-mechanism: firstly,the SPH method is used to simulate the sand flow movement in the sand flow and the local sand clusters are optimized and the kernel function is optimally selected.Secondly,it analyzes the movement of the wind-sand flow under the flat sand bed,and compares the results with the experiment and research,and finally analyzes the movement of the wind-sand flow under the uneven sand bed.The specific content is as follows:(1)The SPH method is optimized for the local particle clustering problem that occurs in the process of simulating the movement of the wind-sand flow.By introducing a tension correction term,a short artificial force is added to the particles when they are stretched or compressed,thereby eliminating the repulsion or attraction between atoms.Optimal selection of SPH method kernel function.(2)The study of the trajectory of sand particles on a flat sand bed shows that the trajectory of sand particles presents a symmetrical and asymmetrical parabolic trajectory.As the wind speed increases,the height and length of the sand particles' jumps increase.As the sand particles rise in the position of the sand bed,the height and length of the sand particles have an increasing trend.Analyzing the movement speed of sand particles,it is concluded that the horizontal speed and vertical speed of sand particles increase with the increase of the position of the sand bed and the increase of the frictional wind speed during the initiation of the sand flow.When the sand particles in the gas reach a certain level,the vertical velocity of the sand particles changes differently.(3)The analysis of the number of sand particles under the flat sand bed shows that the number of sand particles decreases with the increase of height at different times.As the frictional wind speed increases,the number of sand particles generally increases,but the attenuation rate of the number of sand particles decreases.Analyzing the influence of sand particles on gas particles,it is concluded that the gas particles first have local vortices at the front end of the calculation domain and the parts in contact with the sand particles,and the vortices move backwards over time.(4)The high-speed camera is used to analyze the movement trajectory of the sand particles in the wind tunnel.At the same time,a sand collector is used to measure the sand transport rate at different positions on the sand bed.Analyzing the changes of the sand bed before and after the experiment provides experimental verification for the SPH method to simulate the sand movement.(5)The analysis of the movement of sand particles under the uneven sand bed shows that the height and length of the sand particles on the windward slope are higher than the sand particles on the leeward side,and the height and length of the sand particles increase with the increase in height.As the number of slopes on the sand bed increases,the height and length of the sand particle jumps decrease with the position of the slope.According to the statistics of the number of sand particles,the overall take-off and transportation of sand particles at each position of the windward slope increases with the rise of the slope surface position.As the number of slopes increases,the first slope will have a certain protective effect on the subsequent slopes,so the number of sand particles at each position of the slope at the back position is generally smaller than that of the first slope.(6)The analysis of the movement of gas particles under the uneven sand bed shows that different surface forms have different effects on gas particles.The windward slope will lift the gas particles,and the vortex phenomenon is more likely to form on the leeward slope.In the case of multiple slopes,eddy currents are more likely to appear between the two slopes,which is one of the reasons why the sand particles between the two slopes are more likely to jump up.