耗散粒子动力学的一种新的固体壁面边界条件

A new wall boundary condition in dissipative particle dynamics

由于耗散粒子动力学(DPD)粒子间是软势作用,很难施加无滑移的固体壁面边界,为此提出一种新的固体壁面边界条件,该方法是通过给壁面粒子赋予相对流体粒子的虚拟速度,但壁面粒子不能移动,虚拟速度用于计算壁面粒子对流体粒子的耗散力,进而增大流体粒子的耗散阻力,实现壁面无滑移条件.利用新的边界模型模拟了微通道内的Poiseuille流动,得到的微通道内的速度分布曲线表明,该模型实现了壁面无滑移条件;得到的密度和温度分布曲线显示,壁面附近密度波动很小,但当壁面粒子密度大于8.0时,壁面附近流体粒子密度波动较大.模拟结果与Navier-Stokes方程理论解吻合很好,进一步验证了新边界的可行性和DPD程序的正确性.

Because of the soft potential that dissipative particle dynamics （DPD） employs, the boundary conditions are difficult to impose. A new boundary condition was proposed by giving a virtual velocity to the wall particles. The wall particles do not move in the simulation, and the virtual velocity is used in the calculation of the dissipative force between wall particles and fluid particles, which can increase the dissipa- tive force of the fluid particles, thus, the new boundary model can achieve the no-slip boundary conditions. Poiseuille flow was simulated in a narrow channel to demonstrate the validity of this boundary model. The simulation results of velocity, density and temperature distribution in the channel show that the new boundary condition model is an effective way to implement no-slip boundary conditions, and effectively eliminates density fluctuations in the near wall region. But when density of the wall is more than 8.0, the new wall boundary condition will be unable to work well. The good agreements of the simulation results with the theoretical solution of Navier-Stokes equation also verify the validity of the new model and DPD program.