喷动床DEM模拟曳力模型评价

Assessment of drag models in DEM simulations of spouted beds

针对喷动床DEM模拟中的曳力模型选择问题,利用CFD-DEM方法,对几种曳力模型在矩形喷动床模拟中的应用进行了讨论,研究采用标准k-ε模型和Beer&Johnson表达式考虑湍流和滚动摩擦的影响.结果表明:Arastoopour、Sy-amlal&O'Brien和Tsuji模型均可较好地预测流动结构和空隙率、颗粒速度分布,Tsuji模型模拟结果与实验值最为接近;在环隙区,滚动摩阻力矩大于切向接触力矩,滚动摩阻力矩的加入使颗粒轴向速度最大值的预测更加精确;滚动摩阻力矩与颗粒速度梯度两者之间的相互作用,速度梯度起主导作用.

Drag force is one of the major interaction forces in a rectangle spouted bed gas-solid two phase system.Drag models significantly influence the simulation results.Therefore,the influence of different drag models was assessed in computational fluid dynamics（CFD） simulations with the discrete element method（DEM）.In particular,the standard k-ε two-equation model and the Beer Johnson equation were adopted to investigate the influence of turbulence and rolling friction.The results indicated that the Arastoopour,Syamlal O＇Brien,and Tsuji models were able to predict the flow pattern,voidage profiles,and particle velocity profiles inside the spouted bed,while the Tsuji model agreed best with the experimental data.In the annular gap,the rolling resistance torque was larger than the tangential contact torque.And the addition of rolling resistance made the prediction of maximum particle velocity more accurate.It was also noted that the velocity gradient played a critical role in the interaction of rolling resistance torque and the velocity gradient.