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Mechanical Engineering
Caltech
Abstract-
Liquid-saturated flows of particulate materials are ubiquitous in industrial
and geophysical environments, including debris flows, slurries, mining and
milling operations, and sediment transport. Unlike collision-dominated dry
granular flows or sediment-laden liquid flows, this area of multi-phase flow
research combines the mechanics of particle-to-particle interactions with the
inertial effects of both phases and the effect of a viscous fluid. At Caltech,
we have focused on collisional particle pressures, shear stress measurements
and wall-particle interactions. This talk will highlight our efforts in these
areas including our upcoming studies on NASA's low-gravity aircraft.
Many of the current ideas regarding the rheological properties of liquid-solid flows are based on ideas and experiments by R.A. Bagnold from the 1950s. In Bagnold's work, the shear and normal stresses were found to depend linearly on the shear rate in the `macroviscous' regime, but vary quadratically with the shear rate in the `grain inertia' regime. Although Bagnold's work has been cited extensively over the last fifty years, these results appear to be dictated by the design of the experimental facility and secondary flow effects. As a result there is a tremendous need to reexamine our understanding of these flows and to look to new experiments.
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