Validation study on spatially averaged two‐fluid model for gas–solid flows: I. A priori analysis of wall bounded flows

In our prior study (Schneiderbauer, AIChE J, 2017;63(8):3544–3562), we presented a spatially averaged two‐fluid model, where closure models for the unresolved terms were derived. These closures require constitutive relations for the turbulent kinetic energies (TKEs) of the gas and solids phase as well as for the sub‐filter variance of the solids volume fraction (VVF). In this study, we have performed highly resolved TFM simulations of a set of three‐dimensional wall dominated periodic channels. An a priori analysis shows that these closures are able to correctly predict the wall profiles of the sub‐grid drag modification, the TKEs, the turbulent viscosities and the VVF without requiring special wall corrections. Solely the mixing lengths, which is required by the closures, has to be adapted in the vicinity of wall similar to single‐phase turbulence; in particular, the minimum of the filter size and the distance to the wall should be used.