A5

In reacting granular assemblies, the chemical composition and temperature of the interstitial gas frequently vary on length scales that are much smaller than the particles and that cannot be resolved in a DEM/CFD description. This small-scale heterogeneity is induced by irregular flow structures inside the intricately shaped interstitial void spaces between arbitrarily shaped and randomly packed particles and exacerbated by gas phase chemical reactions. Additionally, the material make-up and temperature of an assembly vary not only from particle to particle, but also within a particle, eliciting small-scale variability on part of the gas phase through gas-particle heat and mass exchanges. Particularly if the reaction and transfer rates are nonlinear, the influence of small-scale compositional heterogeneity of the interstitial gas on its resolved large-scale behavior is very difficult to gauge and quantify at present.
In order to address this challenge, our objective is to develop and harness a probabilistic description of the small-scale variability in the gas phase composition that permits an incorporation of realistic chemical kinetics and gas-particle heat and mass exchanges. A particular focus lies on the coupling with the DEM description of a granular assembly and the transfer of intraparticle and interparticle heterogeneity to an underresolved gas flow. Besides obviating the common assumption of small-scale homogeneity, the approach we target aids minimizing the dependency of model predictions on the chosen resolved length scale and promotes universality.