Study On Sand Flux Structure Dynamics Characteristics Based On SPH

Land desertification is becoming more and more serious because of the destruction of natural environment by human beings.One of its consequences,the wind-blown sand disaster has make serious harm to people's daily production and life.And how to effectively control the sand damage has become an urgent problem to be solved.Wind-blown sand flow structure refers to the distribution of wind-blown sand flux in space.It is of great significance to study the wind-sand flow structure while it's used to describe the rule of wind-blown sand movement,and it can provide the key theoretical guidance for the scientific formulation of sand control measures.As a kind of two-phase flow including gas and sand phase,the gas carries the sand particles and provides energy for its movement.At the same time,the sand particles have a negative effect on the gas and change the original one.The gas and sand interact with each other and it forms the movement mechanism of the wind-blown sand flow.In this paper,the smooth particle hydrodynamics(Smoothed Particle Hydrodynamics: SPH)method is used to discrete the gas and sand phase of the wind-sand flow into SPH particles,and the motion model of wind-sand flow which contains the sand and gas two-phase coupling is established,then the wind-blown sand movement is simulated.The condition of force on the sand and gas is the basis of simulating wind-sand movement.In this paper,the motion equation and coupling relationship between wind-sand two-phase are established after analyzing the stress condition of sand and gas in moving process,and the two phases are discretized by SPH method.The different substances use different smooth length in the wind-blown sand flow,and the feedback effect of the sand particles on the wind is included in the calculation process.At the same time,considering the collision between the sand particles,the collision model between the sand particles is established.The selection of some key parameters,such as smooth length,time step,boundary condition setting and so on,in the process of using SPH method to establish wind-blown sand movement model is also discussed,and then the program of the model is implemented.In this paper,the process of sand particle jumping from sand bed to wind-blown sand flow reaching dynamic equilibrium is simulated under the condition of logarithmic flow and the homogeneous sand bed,and the take-off velocity distribution of the leap sand isanalyzed statistically.The relationship between the law of take-off velocity distribution and the distribution of sediment transport along the height is analyzed.