对于A类颗粒,鼓泡流化床中,随着网格尺寸的减小,膨胀高度降低,细网格模拟达到网格无关的值接近于实验数据即网格细化可以预测鼓泡流化床的膨胀高度,但是,当前的计算能力无法达到工业规模反应器的计算要求;流化气速越高,达到网格无关时的网格尺寸越大。与传统的基于平均方法的曳力系数相比,耦合了EMMS厂bubbling曳力系数的双流体(TFM)模型允许使用更粗网格,且准确性大大改善,将为工业化大型反应器模拟提供很好的方法,其中,EMMS/bubbling曳力模型如以前的论文(Shi et a1.,2011)。
The free path of a vibro-fluidized two-dimensional(2D) inelastic granular gas confined in a rectangular box is investigated by 2D event-driven molecular simulation. By tracking particles in the simulation, we analyze the local free path.The probability distribution of the free path shows a high tail deviating from the exponential prediction. The anisotropy of the free path is found when we separate the free path to x and y components. The probability distribution of y component is exponential, while x component has a high tail. The probability distribution of angle between the relative velocity and the unit vector joined two particle centers deviates from the distribution of two random vectors, indicating the existence of the dynamic heterogeneities in our system. We explain these results by resorting to the kinetic theory with two-peak velocity distribution. The kinetic theory agrees well with the simulation result.
