Gas-particle flows are encountered widely in chemical process industries. These flows are often unstable and persistent fluctuations in velocities and particle volume fractions occur over a wide range of length and time scales. It is now well established that two-fluid models (TFM), with constitutive relations for the stresses deduced from the kinetic theory of granular materials, are able to capture the formation of such inhomogeneous structures. However, resolving all these structures in simulations of industrial scale devices is impractical - much like simulating all the scales in turbulent flows is not practical. We have been developing coarse-grained two-fluid models that can be used to simulate large-scale coherent structures, very much in the spirit of Large Eddy Simulation (LES) of turbulent flows. In such models, the consequences of fine structures that have been filtered out appear in the form of residual correlations which must be modeled.In this talk, I will highlight our approach to developing such coarse-grained models and summarize the main results. Briefly, we have performed a large number of highly resolved simulations in periodic domains and systematically filtered the results to extract computational data on the residual correlations, which are then used to deduce constitutive relations. I will also discuss the similarities and differences between the present problem and LES of turbulent flows.
Coarse-grained models of gas-particle flows
Sankaran Sundaresan, Princeton University
Mar 4 2013 - 4:30pm