摘要:
对牛顿流体内溶解双颗粒在垂直管道中的沉降运动进行了直接数值模拟.流体运动由守恒方程计算,密度和黏性的变化考虑流场温度变化的影响,通过积分粘性应力和压力获得颗粒的受力跟踪颗粒运动,溶解引起的相变及其形状的变化由溶解潜热、溶解质量与分散相边界处的温度梯度的关系建立的方程决定.通过颗粒和流体间相互的作用力和力矩及边界条件的施加实现相间耦合.对双颗粒在等温流体无溶解条件和非等温流体溶解条件下的沉降过程进行了计算.结果表明,在一定雷诺数内,热对流产生的颗粒尾迹处涡的脱落以及溶解引起的颗粒质量、颗粒表面形态的变化引起了颗粒的横向摆动,并使颗粒沉降速度发生了变化.
Abstract:
The influence on the motion of single solid particles in a Newtonian fluid by melting and convection is direcly simulated.The fluid motion is computed from the conservation laws.Density and viscosity change with fluid temperature,and the particle moves according to the equation of motion of a rigid body under the action of gravity and hydrodynamic forces arising from the motion of the fluid.In the process of melting,a distinctive morphology develops due to the different heat fluxes around the particle＇s surface, and the thermal gradient determines the melting rate.The phases are coupled by the fluid-particle mutual force,force moment and the boundary conditions.In our study,two different situations are carried out,which are sedimentation in isothermal fluid without thermal convection and melting;sedimentation with thermal convection and melting,two double particles are simulated separately. The results show that the vortex shedding arising by the natural convection,mass losing by melting and melting morphology change the sedimentation velocity and induce horizontal oscillation.
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