Switch Function and Sphericity Coefficient in the Gidaspow Drag Model for Modeling Solid-Fluid Systems

This article presents considerations pertaining to two aspects of numerical modeling of fluid-solid type systems based on the Gidaspow drag model (key part of the Eulerian multiphase model). The first aspect pertains to the so-called switch function; the characteristics of this function are generalized in the article, new computation formulas are given, control coefficients are introduced, and a comparison of numerical simulation results is presented based on the original and modified version of the Gidaspow model. The second aspect pertains to the so-called sphericity coefficient; this article describes methods for determining this coefficient, presents simulation results obtained based on these methods, and suggests the most appropriate variant for the flow system considered. All computations were performed for spouted bed dryers for grain, previously tested under laboratory conditions. The results of numerical simulations for this device were verified. High qualitative and quantitative consistency was achieved; this work was presented in an earlier paper. The objective of the study described in this article was to develop a new mathematical form of the Gidaspow model comprising precise formulations of the switch function and the sphericity coefficient that influence accuracy of the model predictions.