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

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.