【摘要】 采用大涡模拟、Smagorinsky亚格子应力模型及SIMPLER算法,数值模拟了气固两相流体后台阶流动中各物理量的输运特性。首先,讨论了后台阶流动中分离涡旋结构和回流区长度随入口速度分布、台阶上游长度的变化情况;然后,用颗粒追踪法,计算了不同入流速度、不同粒径的颗粒在后台阶流场中的扩散行为。计算结果表明,选择抛物线型入口速度分布,能比较好地模拟真实的后台阶流动;在气固两相流动中,颗粒运动是气相涡旋和固相颗粒惯性共同作用的结果,随着颗粒粒径的增加,颗粒对气体涡旋的跟随性逐渐变弱,而其惯性特性表现得越来越显著。当大量颗粒由不同粒径组成时,颗粒的扩散将具有选择性,显示出多尺度耦合现象。所得结果有助于解释风成地貌形态的形成机理,也可以为风沙流风洞模拟实验设计提供一定的理论指导。更多还原

【Abstract】 The parameters of two dimensional backward-facing step gas-particles flows are studied numerically based on large-eddy simulation,Smagorinsky SGS stress model and SIMPLER algorithm.First,the variations of the reattachment positions of two dimensional backward-facing step with different upper flow channel and inlet velocities are revealed.Then,the solid particles with different diameters are traced by particle trajectory method,and the particle dispersion characteristics at different inlet velocities are disclosed.Results reveal that the particle motion is mainly controlled by its inertia force on the particles with diameter larger than 100 μm,and it is essentially controlled by air force for the particles with diameter less than 20 μm,and by both forces with transitional diameters.The research shows that large-eddy simulation is a powerful method to study the gas-particle two phase flows,and it can be used to guide construction of porous fence and performance of the gas-particle flow experiments in laboratory.更多还原