Abstract:

Drag model plays one of important roles for CFD simulation of multiphase flows. Six drag models proposed by Gidaspow, Syamlal-O Brien, Di Felice, Gibilaro, Dallavalle and BVK are compared for predicting homogeneous liquid-solid fluidization in this study. CFD simulations are conducted based upon a simplified inviscid two-fluid model proposed by Brandani and Zhang in a commercial platform together with user-defined FORTRAN subroutines. Typical experimental data including a wide range of particle Reynolds numbers from reference literatures are employed to evaluate numerical simulation. The results show that either BVK model or Dallavalle model could predict the bed expansion and overall solids holdup very well. The radial profiles of solids holdup predicted by BVK, Syamlal-O Brien as well as Dallavalle model are more accurate, and that the BVK drag model provides better prediction for the radial profile of solids axial velocity. Generally, the BVK drag model demonstrates the best performance for modelling hydrodynamics in homogeneous liquid-solid fluidization as its mechanism is corresponding with the kinetic behavior of particles in liquid-solid system. Taking both prediction accuracy and model complexity into consideration, Dallavalle drag model seems to be the optimal choice among the rest of the drag models.

Key words: multiphase flow, hydrodynamics, CFD, homogeneous liquid-solid fluidization, drag model

摘要：

基于无黏性双流体简化模型在商业化软件平台上，通过增加用户自定义子程序考察了Gidaspow、Syamlal-O’Brien、Di Felice、Gibilaro、Dallavalle和BVK曳力模型对液固散式流态化CFD模拟结果的影响行为，探讨了相应的影响机制。经与文献中不同颗粒Reynolds数的代表性实验数据对比后发现：BVK和Dallavalle曳力模型对床层膨胀高度和整体固含率的预测精度较高；BVK、Syamlal-O’Brien以及Dallavalle曳力模型给出的床内固含率径向分布较为准确；BVK曳力模型较为准确地再现了颗粒轴向速度的径向分布特征。BVK曳力模型的影响机制与液固散式流态化中颗粒动力学特性相符合，在所考察范围内其预测性能最优；Dallavalle曳力模型在其余5个传统模型中预测性能较优且形式简洁在程序中易于实现。

关键词: 多相流, 流体动力学, 计算流体力学, 液固散式流态化, 曳力模型