Suspensions and Granular Media: Wet vs. Dry

California Institute Of Technology, Pasadena CA

Investigators

Abstract

CBET-0828563 Brady Project Summary Intellectual Merit: Suspensions and granular media are found widely in nature and industry. And although the two fields have developed independently, recently it has been noted that viscous suspensions and dry granular materials often display similar flow phenomena. Despite the similarities, the two fields nevertheless remain separate. Here we propose that this separation is unnecessary and that suspensions and granular media - wet and dry - actually correspond to different limiting behaviors of one common system. The linking parameter is the Stokes number - the ratio of the inertial to shear forces: small Stokes numbers correspond to viscous suspensions and high Stokes numbers to dry granular media. The proposed research is a simulation study covering the entire range of Stokes numbers (and concentrations) and thus explores the flow behavior and rheological connection between these two fields. Not only will we learn about this connection, we may also advance our understanding of both suspensions and granular media. This study also provides vital rheological data (shear and normal stresses, shear-induced diffusivities, microstructures, etc.) for inertial suspensions, of which there appears to be surprisingly little. Broader Impact: In a broader context, this research will help elucidate the behavior of an often called new state of matter - granular matter. Granular flow forms part of the larger area of multiphase flow with applications ranging from sediment transport in rivers and bays, to pneumatic conveying of minerals, to the production of pharmaceutical powders. The work will also engage PhD students who will become experts in computational methods, multiphase fluid physics and rheology. This research provides the foundation for modeling multiphase flows that has widespread application in science and technology.