Numerical Modeling Of Wind-blown Sand Motion Based On Stochastic Force Model

There are three modes of wind-blown sand particles in flow field near-surface: creep,saltation,and suspension.The air flow is turbulent,so that it leads the sand particles to move with time and space.Aeolian saltation not only developes the eolian landform,but also causes many natural disasters,which have strong impact on human's normal live.Therefore it is significant to study the aeolian saltation and suspension in the air as a kind of two-phase gas-solid flow.Dased on Langevin equation and the Brownian stochastic force model,this paper proposed a comprehensive stochastic force model to simulate the random factors in air turbulent flow.These factors were equivalent to continuous applied force on particles in the area of stochastic force.In order to simplify the calculation model and obtain accuracy results,a large number of particles was analyzed.The main works of this paper are as follows:(1)Firstly,the model(Langevin equation and stochastic force model)proposed by the aeolian saltation in the literature is analyzed and summarized.An comprehensive stochastic force model based on classical Brownian force is proposed to solve the aeolian saltation on the macro level.(2)Secondly,the theoretical model of sand grain movement including a stochastic force was developed to describe the sand motion.The applicability of the stochastic force model was verified by comparing with other numerical results and field experimental data.An efficient way to generate random numbers was found to produce higher quality Gaussian white noise random number for sand flow simulation.(3)Finally,the modified comprehensive stochastic force model was used to calculate the trajectory,velocity and acceleration of sand particles.Aeolian saltation has been analyzed with sediment runoff and diffusion concentration of fine sand particles.A steady air flow field was reached by considering the coupled action of sand and air flow field.The numerical results are in good agreement with field experimental data.The results show that the comprehensive stochastic force model based on the Brownian force formula is useful in solving the problem of aeolian saltation.