A chimera approach for MP-PIC simulations of dense particulate flows using large parcel size relative to the computational cell size

The Multiphase Particle in Cell (MP-PIC) is an Eulerian-Lagrangian numerical method that resolves the particle-particle interactions using the averages mapped from the Lagrangian parcels onto the Eulerian mesh. The MPPIC's accuracy depends on mesh quality and resolution, but the mesh resolution requirements for the Computational Fluid Dynamics (CFD) fields and MP-PIC models are not in accordance. This paper proposes a chimera approach, which implements two overlapping meshes in the Lagrangian-Eulerian framework with disparate length scales - a fine mesh for the CFD fields and a coarser mesh for the MP-PIC fields. The CFD fields are mapped to the MP-PIC mesh, while the coarse mesh fields, such as solids volume fraction and momentum source of parcels, are mapped to the finer CFD mesh. The National Energy Technology Laboratory's (NETL) Small-Scale Challenge Problems-I (SSCP-I) fluidized bed case is selected for simulations and model validation. A parametric study is conducted, which considers different drag and inter-particle stress models and different solids volume fraction limits. We show that the chimera approach results in a realistic turbulent flow field for accurate drag force calculations on parcels while preserving adequate conditions for the submodels’ validity under MP-PIC. The results are in good agreement with the experimental findings, specifically the pressure drop, Eulerian average particle velocity, and granular temperature. The chimera method is developed to overcome the averaging limitations when the particle size is comparable to the cell size or when particle collisions may not be captured accurately, and a finer mesh is required for the fluid flow.