(54ac) A Fundamental Framework for Simulating Large-Scale Particulate Systems Using the Direct Simulation Monte Carlo Method

Abstract: A hybrid direct simulation Monte Carlo (DSMC) and multiphase particle in cell (MPPIC) scheme is developed to accurately simulate large-scale particulate systems. The MPPIC method tracks parcels that represent a large number of real particles, and can be used to simulate large-scale particulate processes with complex particle-scale physics. Despite the efficiency of the MPPIC method, its usefulness for dynamic systems is limited due to evaluation of the solids stresses and solids heat flux. The DSMC is a fundamental modeling approach that is used to calculate collisions between parcels. In doing so, the DSMC method effectively evaluates the collision integral in the Enskog equation. The DSMC method therefore does not require simplifying assumptions that are often used to derive continuum closures, such as closeness to equilibrium and small Knudsen numbers. The validity of the Enskog equation breaks down as the solids phase reaches the packed limit. Consequently, pure DSMC simulations show errors such as over-packing in dense regions. To eliminate errors associated with over-packing, the MPPIC solids stress model is used when the solids concentration is close to the packed limit and the DSMC method is used for dilute and moderately dense regions. Simulations using the hybridized MPPIC-DSMC method are completed for a homogeneous cooling system, fluidized bed, and rider flow. The new hybrid simulation technique is compared to more traditional methods, such as two fluid modeling, MPPIC, and the discrete element method.