(85f) Simulating Fluid-Particle Flows Across All Flow Regimes

In technological applications and nature, fluid-particle flows often exhibit large variations in the local particle volume fraction. For example, in circulating fluidized beds there are regions where the particles are close-packed as well as very dilute regions where particle-particle collisions are infrequent. Thus, in order to simulate such fluid-particle systems, it is necessary to design a numerical algorithm that can accurately treat all flow regimes that can occur in any particular application. Here, a novel algorithm, based on splitting the kinetic flux dynamically and locally in the flow, is implemented in in an open-source CFD package for particle velocity moments up to second order. In close-packed regions, a traditional hydrodynamic solver is employed, while in dilute to very dilute regions a kinetic-based finite-volume solver based on quadrature-based moment methods is used. The accuracy and robustness of the proposed flux-splitting algorithm is demonstrated using gravity-driven, gas-particle flows exhibiting cluster-induced turbulence. By varying the average particle volume fraction in the flow domain, it is shown that the flux-splitting algorithm handles seamlessly all flow regimes present in circulating fluidized beds.