稀疏颗粒流体系统的微极流体模型描述:以顶盖驱动方腔流为例

MICROPOLAR FLUID MODEL DESCRIPTION FOR DILUTE PARTICLE-FLUID SYSTEM:A CASE STUDY OF LID-DRIVEN CAVITY FLOW

因粒子和流体介质属性不同,稀疏颗粒流体系统常表现出相反的流动增强和减弱行为.为基于一组方程描述稀疏颗粒流体系统相反的流动行为,文章推荐了微极流体模型,并通过对微结构参数(耦合数和无量纲特征长度)的全面分析,尝试给出描述不同流动行为的参数区间.首先,梳理微极流体模型和微结构参数的物理意义,基于OpenFOAM库建立了微极流体控制方程的有限体积离散求解方案,并在一维微极泊肃叶流动中验证了其准确性.随后,基于顶盖驱动方腔流,开展了大范围微结构参数组合下的流体动力学行为计算,分析各微结构参数及其组合对流体速度、微转动、动能以及总能的影响规律.结果表明微极流体模型能够描述稀疏颗粒流体系统呈现的流动增强和减弱行为,且存在一个微结构参数临界区间,当耦合数和无量纲特征长度的乘积N·L<20.48时,微极流体模型可描述流动减弱现象;当N·L>28.16时,可描述流动增强现象.微极流体模型较完备的物理参数使得其在描述不同颗粒流体系统行为时更具普适性,有望扩展颗粒流体系统研究的理论基础.

Due to the different properties of particles and fluid medium,dilute particle-fluid systems often exhibit opposite behaviors of flow enhancement or attenuation.To describe the opposite flow behaviour of dilute particle-fluid systems based on a set of equations,we recommended micropolar fluid model in this paper,and trying to give parameter ranges to describe the different flow behaviors through a comprehensive analysis of microstructure parameters(coupling number and dimensionless characteristic length).First,clarify the physical significance of micropolar fluid model and microstructure parameters,a finite volume discretized solution scheme for micropolar fluid control equations is established based on OpenFOAM library,and its correctness is validated by in a one-dimension Poiseuille micropolar flow.Then,based on lid-driven cavity flow,the hydrodynamic behavior calculations under a wide range of microstructure parameter combinations are carried out,and the influence laws of microstructure parameters and its combinations on the velocity,microrotation,kinetic energy and total energy of fluid are analyzed.The results show that micropolar fluid model is capable in describing the flow enhancement and attenuation behaviors exhibited by dilute granular-fluid system,and that there exists a critical range of microstructure parameters.When the multiply of coupling number and dimensionless characteristic length N×L is less than 20.48,micropolar fluid model can describe the flow attenuation phenomenon,when N×L is more than 28.16,it can describe the flow enhancement phenomenon.The more complete physical parameters of micropolar fluid model make it more generalizable in describing the different behaviors of particle-fluid systems,and it is expected to extend the theory foundation for the study of particle-fluid systems.