基于格子玻尔兹曼方法的单孔射流鼓泡床的离散颗粒模拟

利用基于格子玻尔兹曼方法的离散颗粒模型对单孔射流鼓泡床进行了研究. 此算法基于四向耦合的离散颗粒模型, 流体的控制方程采用考虑了孔隙率和流固相的滑移速度对流体流动影响的修正格子玻尔兹曼方法来求解, 颗粒间相互作用通过时驱硬球模型求解, 流固耦合采用EMMS曳力模型. 首先研究了不同颗粒对形成气泡大小的影响, 结果表明, 在相同的射流气速下, 粒径越大形成的气泡越小. 在粒径相同的情况下, 提高气体的入射速度, 则形成的气泡越大. 同时考察了气泡的分离时间与粒径以及射流气速的关系, 结果表明, 随着粒径以及射流气速在一定范围内的改变, 气泡的分离时间并没有明显改变. 另外颗粒床层扩展影响气泡形状, 颗粒床层变宽后, 气泡的形状接近于圆形; 颗粒床层高度增加时, 气泡明显变小. 最后考察了气泡诱导现象, 模拟发现当区域有空腔时, 气泡会被诱导到空腔的方向.

Discrete particle simulation of bubbling bed with jet flow at a single orifice based on the lattice Boltzmann method

This paper presents a discrete simulation of bubbling bed with jet flow at a single orifice using a lattice Boltzmann method based discrete particle model proposed by us. This algorithm is based on four-way coupling discrete particle simualtion whereas governing equations of fluid flow solved by modified lattice Boltzmann method with consideration of the effect of porosity and relative slip velocity between particle and fluid and interaction between particles modelled by time-driven hard-sphere model. The EMMS drag model is adopted for coupling between solid and gas phase. We first investigated the influence of particle diameter and gas jet velocity on bubble formation. The results show that bubble size reduces with increasing of particle diameter under the same gas injet velocity, while bubble size increases with increasing of gas jet velocity. Then the relationship of bubble detached from the bottom of bed with particle size and jet flow rate is explored. The results show that with the change of particle size and jet flow rate, bubble detached time is almost the same. We also found that the enlargement of solid initial bed has an effect on bubble size and shape. The bubble tends toward a circular shape with a wider bed of solids and become smaller with increasing of solid initial bed height. Finally we reproduced the phenomenon of bubble inducement that bubble tends move toward an empty region.