三维球形堆积床内湍动特性的数值模拟

Simulation on Turbulence Characteristics in Three-Dimensional Sphere Packed Bed

采用离散元软件LIGGGHTS重现球形堆积床的重力堆积过程,建立了球形堆积床的三维随机结构模型,同时构建了顺排结构和插排结构两种有序堆积模型与之对比.采用CFD软件Fluent14.0对三种结构堆积床内的湍流流动进行了数值模拟研究.通过宏观阻力系数和压强降的分析,验证了随机模型的有效性,并讨论了球形堆积床随机结构内速度场特性和湍流参数的变化规律.结果表明:与经典的Ergun公式相比,随机模型的宏观阻力系数和压强降的整体误差低于6%;与有序堆积床相比,随机堆积模型具有流体速度场均匀性好、尾旋尺寸大、扰动强烈及瞬时耗散率极值高等特点.

Discrete element software LIGGGHTS is introduced to reproduce the forming process of sphere packed bed by gravity,and a 3 D random geometric model similar to the actual accumulation structure is presented. Two ordered models,the in-line packed model and the staggered packed model,are also established to contrast with the random packed model. CFD software of Fluent 14. 0 is employed to study the turbulence flows in the packed bed. The effectiveness of the random model is validated by analysis of the macroscopic pressure drop and the resistance coefficient,and the velocity field and the turbulence parameters of the three structures are predicted and discussed. Simulation results show that the macroscopic resistance coefficient and the macroscopic pressure drop of the random packed bed model are consistent with the classical formula of Ergun,with maximum relative error less than 6%. Compared with the orderly packed bed,the random packed model is characterized with more homogeneous velocity field,larger tail vortex size,stronger disturbance and extremely larger turbulence dissipation.