基于DEM模拟的气固鼓泡床内流场间歇性及颗粒相干结构的分析

采用计算流体力学和离散元方法（CFD-DEM）对气固鼓泡床流动行为进行模拟研究，并基于模拟结果分析鼓泡床内气泡和颗粒微观运动特性。对颗粒速度的脉动能谱进行分析，发现鼓泡床流场中存在间歇性。通过对比鼓泡床不同轴、径向位置的颗粒脉动速度的平坦因子，发现鼓泡床内不同位置的流场间歇性不同，随着床层高度的增加，流场的间歇性减弱；在径向上，过渡区的流场间歇性明显大于边壁区和中心区。进一步采用连续小波分析方法揭示了相干结构（颗粒涡团）的分布以及演化过程，并分析了不同尺度下相干结构（颗粒涡团）的分布与鼓泡床内颗粒与气泡运动的关系。

Analysis of flow field intermittency and coherent structure of particles based on DEM simulation of gas-solids bubbling bed

The gas-solids flow in a bubbling bed was simulated by the combination approach of computational fluid dynamics (CFD) and discrete element method (DEM), and the simulation results were used to investigate the microscopic characteristics of bubbles and particles. The particle fluctuating energy spectrum was calculated to find out the flow field intermittency in the bubbling bed. Different features of flow field intermittency were found at different locations of bubbling bed by comparing the flatness factor of fluctuation velocity of particles. With increasing bed height, flow field intermittency was weakened. Along the radial direction, the flow field intermittency in the transition region was stronger than that in the wall and center region. Continuous wavelet transform was used to investigate the coherent structure of particles and its evolution process, as well as the relation between coherent structure of particles and flow behavior of bubbles and particles on different scales.