直接模拟中不同边界条件的实施及对沉降规律的影响

在牛顿流体中, 对颗粒在4种不同边界的垂直通道中的沉降运动进行了直接数值模拟. 计算结果表明:通过计算区域随颗粒运动而移动构建的无限长通道能准确模拟颗粒自由下落到稳定沉降的发展过程; 周期性边界条件由于流场变化, 对颗粒沉降产生了影响, 不能模拟颗粒的自由沉降过程; 底部封闭边界适合模拟封闭容器内颗粒与固壁的相互作用过程, 若颗粒达到稳定沉降, 也能模拟无限长通道内的沉降过程; 流化边界适合模拟流化床内气固两相流动. 计算结果有助于更好地理解和使用不同边界条件. 关键词： 直接数值模拟 边界条件 沉降 任意拉格朗日-欧拉方法

The implement and influence of different boundary conditions in direct simulation on particle sedimentation

In this paper, we present a direct numerical simulation of particle sedimentation in two-phase flow with four different boundary conditions. We demonstrate that different boundary conditions can result in quite different flow behaviors. Some interesting results are obtained. By redefining the computational domain at each time step according to the position of the particle, we construct an infinite channel, which can simulate the particle sedimentation accurately; the flow pattern of periodic boundary is quite different from the infinite channel because of the disturbed flow field; if the settlement is reached steadily before the closed bottom, the closed channel can also simulate the particle settled in the infinite channel; the fluidized condition slows down the particle sedimentation, which is very helpful for better using the boundary conditions.
Keywords： direct numerical simulation boundary condition sedimentation arbitrary Lagrangian-Eulerian technique