气固两相流中颗粒碰撞的Monte-Carlo数值模拟

Monte-Carlo numerical simulation of inter-particle collisions in gas-solid flows

利用颗粒碰撞动力学模型和颗粒几何碰撞率模型,采用Monte-Carlo算法来模拟颗粒之间碰撞,把该算法与求解雷诺应力-概率密度函数模型的有限差分-MonteCarlo算法耦合起来,对轴对称突扩通道内的两相旋流场进行了数值模拟,模拟结果表明,由于颗粒碰撞使颗粒的动能和湍动能在三个坐标方向上进行了再分配,从而导致颗粒的动能和湍动能在三个坐标方向上趋于各向同性;另外,由于颗粒碰撞破坏了颗粒-颗粒、颗粒-流体微团之间的速度关联,从而造成颗粒湍动能及两相速度脉动关联的降低。

Making use of inter-particle collisions dynamics and probability of inter-particle collision, a Monte-Carlo arithmetic is set up to take into account inter-particle collisions, which is coupled with a hybrid finite-difference-Monte-Carlo numerical arithmetic that is proposed for Reynold stress model (RSM)-probability density distribution function (PDF) two-phase turbulence model. This hybrid arithmetic is used to simulate a swirling gas-particle flows which take place in a axial symmetry and suddenly expanded pipe. The result of numerical simulation shows: (1) inter-particle collisions redistribute kinetic energy and turbulence kinetic energy of particle in three coordinate directions, as a result, the distribution of those energy inclines to isotropy; (2) because inter-particle collisions destroy the fluctuation velocity correlation of particle-particle and particle-gas, turbulence kinetic energy of particle and fluctuation velocity correlation of particle-gas phase decrease.