中文摘要：

为模拟具有复杂几何结构的气固流动系统，文中将计算流体力学和离散单元法与边界元方法结合起来，对沉浸管式流化床内颗粒及气泡的运动行为进行了数值模拟。模拟计算得到的瞬态流型图揭示了气泡绕流沉浸管束时出现的合并和破碎状态及颗粒群的详细运动行为，发现床内气固二相的流动受到沉浸管束存在的显著影响。当颗粒及气相的流动受到沉浸管的阻碍而绕管流动过程中气泡会发生变形，变得扭曲狭长且易被撕碎。同时颗粒与管道壁面碰撞会造成气固二相复杂的动态运动形式，床内的管道大部分时间会被气穴包围，将严重阻碍管道与颗粒之间的传热。

英文摘要：

In order to simulate the gas-solid flow with complex geometry, the boundary element method （BEM） was incorporated into the implementation of a combined model of computational fluid dynamics （ CFD ） and discrete element method （DEM）. The hydrodynamics in a fluidized bed with immersed tubes was simulated by this method. The transient simulation results showed the dynamics of particles and bubbles. The bubbles coalescence and breakup behavior were successfully predicted when they pass the immersed tubes. The gas-solid flow pattern in the fluidized bed was changed greatly thanks to the immersed tubes. The gas bubbles would be deformed when particles and gas flow are blocked by the immersed tubes. The collisions between particles and tubes will make tubes be surrounded by air pocket in the most of the time, which is disadvantage for the heat transfer between particles and tubes.