AN IMPROVED μ(I) RHEOLOGY MODEL FOR DENSE GRANULAR FLOW IN MOVING BEDS AND ITS APPLICATIONS

Moving bed technology of dense granular flow has been widely applied in industrial processes. A practical simulation method and detailed studies on the characteristics of granular flow in moving bed are of great significance for its design and operation. In this paper, an improved μ(I) rheology model for dense granular flow in moving beds is presented. Specifically, the relationship among local particle volume fraction, local granular pressure and granular flow density, is proposed, based on which the governing equations by treating the dense granular flow as a compressible pseudo-fluid are established. The particle-wall shear slip boundary condition, together with the regularisation method in the calculation of pseudo-fluid viscosity and granular pressure are presented as well. Firstly, the proposed model is validated and the rheological parameters involved in μ(I) model are determined by the experimental results of velocity distributions for 3 kinds of typical granular materials, namely, glass beads, corundum beads, and coarse sand in a silo. Detailed results regarding the particle velocity, solid volume fraction, velocity shear rate and inertial number of the 3 different granular flow in the silo are obtained. The two typical different flow modes, i.e. the funnel flow for coarse sand and the mass flow for glass beads in silos, are well predicted. Secondly, the granular flow of glass beads passing through a moving bed with an inbuilt pipe is studied as well. Reasonable results including particle velocity, solid volume fraction and granular pressure around the pipe are revealed and analyzed. The typical solid volume fraction of the studied cases ranges from 0.510 ~ 0.461, and the inertial numbers in most region of the beds are less than 0.1. The simulated results show that the proposed model is feasible for dense granular flow in moving beds and the calculation amount is significantly reduced compared with that of the multi-phase simulation method.