Abstract:

The modified lattice Boltzmann method (LBM) and discrete element method (DEM) were combined to simulate the bubble movement in bubbling bed of single port jet, based on the LBM-DEM four-direction coupling model. Fluid phase used the classical D2Q9 model of LBM, particle phase was solved by the discrete element soft sphere model, particle drag force was solved by adopting the Gidaspow model, and fluid-solid coupling was based on the Newton's third law. The above model was solved by the Fortran language procedure. The bubble evolution process in bubbling bed was simulated and compared with the related experiments, which effectively verifies the accuracy of the present model. Meanwhile, the particle velocity, particle volume fraction and energy distribution in the bed were analyzed. The results show that the distribution of particle time-averaged velocity can show the motion strength of particles, and reflect the bubbles' movement process. The voidage in the bed and the distribution of particle volume fraction have the high consistency in predicting the bed expansion height. The initial accumulation effect makes that potential energy of particles is always larger than kinetic energy of them in the bed. In addition, potential energy increases, but kinetic energy gradually decreases with particle density.

Key words: two-phase flow, lattice Boltzmann method, discrete element method, fluid-solid coupling, numerical simulation

摘要：

将修正后的格子Boltzmann方法（LBM）与离散单元法（DEM）相结合，建立LBM-DEM四向耦合模型对单口射流鼓泡床中气泡运动进行模拟。其中，流体相采用格子Boltzmann方法中经典的D2Q9模型，颗粒相求解采用离散单元软球模型，颗粒曳力求解采用Gidaspow模型，流固耦合基于牛顿第三定律。应用Fortran语言编程对上述模型进行求解，模拟得到了鼓泡床内气泡演化过程，并与相关实验进行对比，有效验证了当前模型的准确性。同时，分析了床层内颗粒速度、颗粒体积分数以及能量分布。结果表明：颗粒时均速度分布不仅能体现颗粒运动强弱，也可以反映气泡运动过程；床内空隙率与颗粒体积分数分布在预测床层膨胀高度上具有高度的一致性；初始堆积效应使得床内颗粒势能始终大于颗粒动能；随颗粒密度增加，势能增大，动能逐渐减小。

关键词: 两相流, 格子Boltzmann方法, 离散单元法, 流固耦合, 数值模拟