粗糙颗粒动理学及稠密气固两相流动的数值模拟

考虑颗粒碰撞过程中摩擦作用,给出了粗糙颗粒碰撞动力学.引入颗粒相拟总温来表征颗粒平动和转动脉动能量的特征.基于气体分子运动论,建立颗粒碰撞中平动和旋转共同作用的粗糙颗粒动理学,给出了颗粒相压力和黏度等输运参数计算模型.运用基于颗粒动理学的欧拉-欧拉气固两相流模型,数值模拟了流化床内气体颗粒两相流动特性,分析了颗粒旋转流动对颗粒碰撞能量交换和耗散的影响.模拟得到的流化床内径向颗粒浓度和提升管内颗粒轴向速度与他人实验结果相吻合.模拟结果表明随着颗粒浓度的增加,颗粒相压力和能量耗散逐渐增加,而颗粒拟总温先增加后下降.随着颗粒粗糙度系数的增加,床内平均颗粒相拟总温和能量耗散增加,表明颗粒旋转产生的摩擦将导致颗粒旋转脉动能量的改变,影响床内气体-颗粒两相宏观流动特性. 

KINETIC THEORY OF ROUGH SPHERES AND NUMERICAL SIMULATION OF DENSE GAS-PARTICLES FLOW

The collisional motion of rough particles is analyzed in consideration of translational and rotational motions of particles.The particle average fluctuation kinetic energy is introduced to measure the fluctuating translational and rotational energies of particles.Kinetic theory of rough spheres is proposed on the basis of the kinetic Boltzmann-Enskog equation.The models for solids pressure and viscosity of particles are derived by the Chapman-Enskog method for gas kinetic theory.Flow behavior of particles is simulated using a gas-solid two-fluid model by taking into the effect of particle rotational motion on the interphase energy exchange and dissipations account.Simulated solids concentrations in a bubbling fluidized bed and axial velocity of particles in a riser are in agreement with experimental data published in literature.While the fluctuation kinetic energy increases,reaches maxima,and then decreases as the concentration of particles is increased.With the increase of tangential restitution coefficient,the particle fluctuation kinetic energy and energy dissipation is increased. These indicate that the frictions caused by the particle rotation alter fluctuating energy of particles,which influences the flow behavior of particles in bubbling fluidized beds.