(172c) Important Length Scales in Dense Gas-Particle Flows

There
is a long history of studies on application of dimensional analysis to develop
scaling relations that can be employed for scale-up and scale-down of
gas-particle fluidized beds. It is now well established that two-fluid models
(TFM), with constitutive models for the stresses deduced from the kinetic
theory of granular materials, are able to capture the formation inhomogeneous
structures over a wide range of time and length scales. As resolving all these
structures in simulations of industrial scale devices is impractical, filtered
models that average over small-scale structures are currently being developed.
This has brought to the surface the issue of relevant length scales in
gas-particle flows.

In this
talk, we will review the various length scales that naturally enter in
gas-particle fluidized beds and discuss how an understanding of these scales is
being used to construct simplified filtered models. A dimensional analysis of
these filtered models then suggests a simple set of dimensionless groups that
are important to capture the dynamics of such devices when simulated on coarse
computational grids. Finally, we present simulation results, using both a TFM
and an Euler-Langrange model, which support our choice of dimensionless
parameters.