热对流条件下固液密度比对颗粒沉降运动影响的直接数值模拟

Direct numerical simulation on the influence of solid-liquid density ratio on the particle sedimentation under thermal convection

本文应用任意拉格朗日-欧拉(ALE)算法对固液两相流流场中考虑热对流的非等温颗粒在竖直通道中的沉降运动进行了数值模拟.在牛顿流体中通过积分黏性应力和压力获得颗粒的受力跟踪颗粒运动,使用有限元方法数值求解流场的N-S方程和能量方程,模型不需经验假设.通过模拟来研究颗粒沉降的运动规律和热对流下固液密度比对固液两相流的影响作用.结果表明随着固液密度比的增加,颗粒经历了稳定沉降、周期性摆动,不规则摆动等过程;热对流使颗粒的摆动幅度和沉降速度发生变化;热对流对颗粒的影响作用随着固液密度比的增加而减小.

The arbitrary Lagrangian-Eulerian technique was used in the direct numerical simulation of the sedimentation of particle with thermal convection between parallel walls. The fluid motion is computed from the Navier-Stokes equation and energy equation using the finite-element method. The particle was tracked according to the equations of motion of a rigid body under the action of gravity and hydrodynamic forces arising from the motion of the fluid, the model was used without former experience or presumption. There sults shows that the particle experiences different regimes of motion： steady motion with and without overshoot and weak, strong and irregular oscillations. The thermal convection changes the sedimentation velocity and the oscillation amplitude of the particle,and the impact of particle by the thermal convection was decreased with solid-liquid density ratio increasing.