应用DSMC方法研究烟幕颗粒的撞击扩散特性

Application of DSMC method to study the impact diffusion characteristics of smoke particles

为研究烟幕撞击喷撒过程中颗粒的扩散特性，依据颗粒碰撞动力学理论，建立了烟幕撞击扩散动力学模型，采用直接模拟 Monte Carlo 方法进行数值模拟，分析了气相流场、烟幕颗粒速度场及其浓度分布规律。结果表明，DSMC 方法能够有效的模拟烟幕颗粒的运动与碰撞过程；烟幕射流碰撞后发生转向，其速度减弱约65％～75％，以近似球顶锥体的形态逐步向外扩散；烟幕浓度的极大值集中在射流及碰撞区，在此区域外，烟幕颗粒的碰撞效应减弱，随机扩散作用使烟幕的浓度梯度随高度增加迅速减小，烟幕颗粒的空间分布也变得更加均匀。

In order to study the dispersion characteristics of smoke particles in the process of smoke-screen by pneumatic spray,a discrete particle motion-collision decoupled model was developed on the basis of particle collision dynamics to describe the formation process of smokescreen.The Direct Simulation Monte Carlo （DSMC）method was used to simulate the collision of smoke particles with the gas-phase flow field, smoke particle velocity field and concentration distribution carefully examined.It is shown that the method decently simulate the particle motion and collision.The smokescreen jet flow divagates the initial direction, formes upward field with the velocity that reduced to 65%-75% original after collision,and spreades out-ward gradually with the shape approximately like a spherical cone.The smoke concentration reaches the maximum value in the jet and collision zone,while the collision effect of smoke particle gradually weakened outside of this area,so the smoke concentration gradient increases with height decreases rapidly because of the random diffusion effect,and the spatial distribution of smoke particles become more uniform.