Experimental Investigations On Particle Behavior And Turbulence Burst Over Several Surfaces In A Wind Tunnel

Current investigations on sand particles movement of aeolian research over complex terrain are not perfect.Most sand transport models and wind tunnel experiments are carried out on flat terrain.But the terrain in nature is usually complex,which may have influence on wind field and sand transport process.Therefore,flat-terrain-based numerical models and theoretical analysis on sand particles movement could not exactly predict wind-blown sand movement in natural environment.In this paper,we build a 2-D triangle model of Barchan,which is the most typical sand dune in nature,to investigate the sand particles movement over this triangle model.Then we used PDA to measure particles' velocity over slope and PIV to measure airborne particles in wind tunnel.Base on experimental data,we can get the pattern of sand particles movement,particles' diameter distribution and particles' turbulence intensity over slope surface.Also,we studied the turbulence burst over several terrains by Mu-level method.The main achievements are as following:1.Using PDA to measure saltation particles velocity on windward slope and leeward slope.Summarize the pattern of saltation particles,and the probability distribution of saltation particles,particles' diameter and saltation angles are given over windward and leeward slope surface.The relation equation between particles' mean velocity and slope gradient is given.Also summarize the pattern of particles turbulence intensity over leeward slope surface.2.Using PIV to measure airborne particles in leeward slope region,and summarize the pattern of the particles mean velocity along with the wind velocity or height and put forward the relation equation of them.The probability distribution of airborne particles and particles' diameter are given.The relation equation of upward and downward particles' mean velocity and diameter along with the wind velocity are given.The relation equations of sand emission rate with wind velocity and emission particles' diameter with wind velocity are given.3.Using 1-D Hot wire detector to measure the wind velocity over four different terrains,and summarize the pattern of Reynolds stress and Turbulence intensity variation.The frequency of turbulence burst over four different terrains is compared with each other and the differences are analyzed.In this paper,the pattern of sand particle movement from windward slope surface to leeward slope surface are analyzed and summarized.Also the position over slope has an influence on sand particles movement.The distribution functions we made are useful and helpful to numerical simulation of wind-blown sand movement.The patterns summarized in this paper are are significant to theoretical analysis.The achievements of this paper are very helpful to the sand movement study.