Impact of Contact Scaling and Drag Calculation on the Accuracy of Coarse‐Grained Discrete Element Method

Nico Jurtz,Harald Kruggel-Emden,Ravindra Aglave,Oleh Baran,Ray Cocco,Matthias Kraume

doi:10.1002/ceat.202000055

Abstract

AbstractThe accuracy of coarse‐grained discrete element method (CGDEM) relies on appropriate scaling rules for contact and fluid‐particle interaction forces. For fluidized bed applications, different scaling rules are used and compared with DEM results. The results indicated that in terms of averaged values as mean particle position and voidage profile, the coupling of computational fluid dynamics and CGDEM leads to accurate results for low scaling factors. Regarding the particle dynamics, the approach leads to an underestimation of RMS values of particle position indicating a loss of particle dynamics in the system due to coarse graining. The impact of cell cluster size on drag force calculation is studied. The use of energy minimization multiscale drag correction is investigated, and a reduced mesh dependency and good accuracy are observed.

Highlights

IntroductionCommon applications are heterogeneous catalysis, drying processes, polymerization, and coal combustion or gasification
Fluidized particulate systems are widely used in the chemical and process industry
The question arises which length scale should be used for CFDCGDEM simulations: the diameter of the original particle or that of the CG-parcel diameter? If the latter is possible without loss of accuracy, this would further increase the performance boost due to coarse graining, since a reduced number of particles need to be tracked, and the time step size for the simulation could be enlarged

Summary

Introduction

Common applications are heterogeneous catalysis, drying processes, polymerization, and coal combustion or gasification. Those applications are most often conducted in fluidized beds. This reactor type is characterized by physical phenomena acting on different length scales. The microscopic scale is determined by collisions between individual particles and between particles and the wall, as well as interactions between particles and the fluid phase. The microscale interactions significantly control energy, momentum, and mass transport and lead to local mesoscale phenomena like cluster and bubble formation and, in the case of nonspherical particles, a preferred particle orientation [1]. Those phenomena significantly affect mixing characteristics and flow regime [2, 3]

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