Filtered two-fluid models of fluidized gas-particle flows: New constitutive relations

New constitutive relations for filtered two-fluid models (TFM) of gas-particle flows are obtained by systematically filtering results generated through highly resolved simulations of a kinetic theory-based TFM. It was found in our earlier studies that the residual correlations appearing in the filtered TFM equations depended principally on the filter size and filtered particle volume fraction. Closer inspection of a large amount of computational data gathered in this study reveals an additional, systematic dependence of the correction to the drag coefficient on the filtered slip velocity, which serves as a marker for the extent of subfilter-scale inhomogeneity. Furthermore, the residual correlations for the momentum fluxes in the gas and particle phases arising from the subfilter-scale fluctuations are found to be modeled nicely using constitutive relations of the form used in large-eddy simulations of single-phase turbulent flows. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 3265-3275, 2013