(479d) Validating Segregation Rate Models

Segregation is a difficult problem that has attracted significant attention over the years. One promising avenue for academic progress that might translate into industrial practice is the development of model for segregation rates based on material properties and flow conditions. One significant hindrance to model development, however, is the inherent difficulty in measuring segregation rates (especially in an experimental setting). In the present work, we seek to establish an "equilibrium" between segregation and flow perturbation in free surface granular flows in order to overcome this experimental hurdle. That is, by using periodic flow inversions via an axially-located baffle (in a tumbler-type mixer), we hope to alter the steady-state distribution of particles whereby there exists a balance between the rate of segregation and the perturbation rate. In this way, we can combine the segregation rate expressions that we are interested in testing with our previously developed segregation control framework such that knowing the perturbation rate, we can deduce the segregation rate (much like knowing an equilibrium concentration, along with a reverse reaction rate, one can deduce the rate of the forward reaction). Here we examine binary segregation rate models, both computationally and experimentally, that are appropriate for free surface flows of granular materials. We start with well established models for both size segregation and density segregation and compare these to new and proposed models. This work may have an economic impact on a variety of industries that deal with particle segregation.