Improvement of EMMS drag model for heterogeneous gas-solid flows based on cluster modeling

摘要

Cluster sub-models are developed and combined with the Energy minimum multi-scale method (EMMS) drag model to improve drag predictions for heterogeneous gas-solid flows. Theoretical cluster sub models are developed to relate the cluster parameters with the local solid volume fraction. The cluster sub-models are validated by experimental data in the literatures. Drag coefficients predicted by the modified EMMS model with cluster sub-models are much lower than previous EMMS results and agree well with the experiment-based model. At solid volume fractions between 0.1 and 0.15 the drag coefficient, beta, reaches a minimum at a maximum for slip velocities and gradually increases towards both sides to that of uniform flow. The modified EMMS drag model is further verified by CFD simulations of gas-solid flows in a CFB riser by coupling with the two-fluid model. The verification of the modified EMMS model once again demonstrates the applicability of the cluster sub-models. (C) 2015 Elsevier Ltd. All rights reserved.