(210a) MFIX-Exa: CFD-DEM Simulations of Thermodynamics and Chemical Reactions in Multiphase Flows

Carbon capture and storage technologies based on chemical looping reactors (CLRs) offer a promising approach to decreasing CO₂ emissions from energy production and various industrial processes. Large-scale commercial deployment of carbon capture technologies requires scaling up from laboratory to industrial systems. This large separation of scales is known to be fraught with issues, particularly for the multiphase reactors at the core of these systems. Computational tools can help bridge this gap; therefore, we created MFIX-Exa [1, 2], a modern, massively parallel code for the numerical solution of chemically reacting gas-solids flows in complex reactor geometries. The fluid is modeled using a low Mach number formulation with a multicomponent ideal gas equation of state which is imposed as a constraint of the velocity field. The fluid equations are discretized using an embedded boundary-aware Godunov scheme with an approximate projection. Particles can be represented using a discrete element method (DEM) or with a lower-fidelity particle-in-cell (PIC) approach. DEM employs a soft-sphere spring-dashpot model and is evolved using a forward Euler method with subcycling. Conversely, the PIC model uses a continuum stress to approximate collision forces on parcels that represent statistical collections of real particles. The fluid and particle models are coupled through a volume fraction field in addition to interphase mass, momentum, and energy transfer. Additionally, MFIX-Exa contains a novel “PIC to DEM” application that converts PIC simulation checkpoint files into high-quality initial conditions for computational fluid dynamics-discrete element method (CFD-DEM) simulations. This talk describes the MFIX-Exa model and numerical approach and showcases several verification and validation tests in addition to weak scaling performance results.

[1] Musser, J., Almgren, A.S., Fullmer, W.D., Antepara, O., Bell, J.B., Blaschke, J., Gott, K., Myers, A., Porcu, R., Rangarajan, D., Rosso, M., Zhang, W., Syamlal, M., 2021. Mfix-exa: A path toward exascale CFD-DEM simulations. The International Journal of High Performance Computing Applications. doi: 10.1177/10943420211009293

[2] Porcu, R., Musser, J., Almgren, A., Bell, J., Fullmer, W., Rangarajan, D., 2023. MFIX-Exa: CFD-DEM simulations of thermodynamics and chemical reactions in multiphase flows. Chemical Engineering Science. doi: 10.1016/j.ces.2023.118614