摩擦-动力应力模型研究喷动床内气固两相流动过程

Simulation of gas-solids flow in spouted beds from frictional-kinetic stresses model

考虑颗粒滑动的半持续性接触应力和颗粒碰撞瞬时接触应力对颗粒相应力的贡献,建立了喷动床内气体颗粒两相流动计算模型。采用颗粒动理学和Johnson等的摩擦应力模型,数值模拟喷动床颗粒流动过程,获得了喷动床喷射区、环隙区和喷泉区内颗粒流动特性。模拟计算与He等的实验结果进行了对比。同时分析了摩擦应力模型对颗粒相黏度变化的影响,表明中速颗粒流的颗粒相摩擦应力模型将直接影响喷动床气体颗粒两相流动的预测。

Flow behavior of gas and particles was simulated in the spouted beds by using an Eulerian- Eulerian two-fluid model on the basis of kinetic theory of granular flow. The frictional-kinetic constitutive model for dense assemblies of solids was incorporated. The kinetic stress was modeled by using the kinetic theory of granular flow, while the friction stress was from the combination of the normal frictional stress model proposed by Johnson et al to account for strain rate fluctuations and slow relaxation of the assembly to the yield surface. An inverse tangent function was used to provide a smooth transition from the plastic and viscous regimes. The distributions of concentration, velocity and granular temperature of particles were obtained in the spouted bed. Calculated particle velocities and concentrations in spouted beds were in agreement with experimental data obtained by He et al . Simulated results indicated that prediction of flow behavior of particles was affected by frictional model of particles used in the numerical simulations of spouted beds.