(590e) A Structure-Based Drag Model for Coarse-Grid Euler–Lagrange Simulations

Meso-scale drag force models, also known as filtered drag force models, are required in coarse-grid Euler–Euler (EE) and Euler–Lagrange (EL) simulations of gas-particle flows due to the unresolved flow structures. Coarse-grid simulations adopt larger grid size for the fluid phase relative to the fine-grid simulations, in which the grid size is as small as three to five times of the particle diameter. In the EL framework, coarse-grid simulations still track the location and the velocity of each individual particle. Many efforts have been devoted to the development of models for the meso-scale drag force in coarse-grid EE simulations in the literature. This work, however, aims to propose a model for the meso-scale drag force that can be used in coarse-grid EL simulations. In EL simulations, the complete details of particles in each coarse grid are known and are used to estimate the meso-scale drag force. The proposed drag model makes use of the sub-grid solid volume fraction and the sub-grid velocity of the solid phase. These information can be readily obtained by mapping the known particle position and particle velocity to the sub-grids. The sub-grid gas velocity is calculated based on a simple pressure drop balance assumption among sub-grids. Previous literature shows that the drift velocity correlates well with the meso-scale drag force and accurate correlations between the drift velocity and the meso-scale drag force have been established. In this work, the drift velocity is obtained using the predicted sub-grid gas velocities and the sub-grid solid volume fractions. Furthermore, a priori assessment of the present model is presented. To measure the model’s predictability of the heterogeneity of the flow structure, a scaled drag force is defined as the ratio of the meso-scale drag force to the micro-scale drag force. It is found that the Pearson correlation coefficient between the predicted scaled drag force and the exact scaled drag force reaches around 0.7. Hence, it is concluded that the present structure-based model is promising in estimating the meso-scale drag force in coarse-grid EL simulations.