(212g) A Numerical Model for the Flow Including Dense Solids with Large Size Difference

In a large number of applications of fluidized bed such as gasification, combustion, separation and granulation, the size of solids is not uniform and large objects are coexisting with small emulsion solids.  The size-difference induces characteristic motion of solids and results in segregation and mixing phenomena.  It is difficult to treat these systems by existing numerical models and, in the present study, a numerical model which expresses the motion of large objects in gas-fluidized beds is proposed.  The present model is based on DEM-CFD mesoscopic model and inspired by volume penalization method (Kolomenskiy & Schneider, J. Comput. Phys., 2009), one of the methods for the direct simulation of solid-flow systems.  The interaction force between fluid and large object is estimated by assuming that large object is consisted of dense small particles, fictitiously.  In this study, the motion of a large sphere in a bubbling fluidized bed is demonstrated and results are compared with experiments.