A new instability mode in fluidized beds

It is shown that the state of "isothermal"homogeneous fluidization can be linearly unstable to small-amplitude "non-isothermal" disturbances transverse to the direction of gravity. Conditions for instability of this new mode are examined and the marginal stability conditions are derived. The underlying physical mechanism of the instability is discussed and contrasted with the widely known particle-phase-inertia-driven longitudinal modes of planar instability voidage waves

Slide Conveying of Granular Materials-Thinking Out of the Glovebox

The vibratory conveyor, routinely employed for normal-gravity transport of granular materials, usually consists of a continuous open trough vibrated sinusoidally to induce axial movement of a granular material. Motivated in part by a hypothetical application in zero gravity, we propose a novel modification of the vibratory conveyor based on a closed 2d trough operating in a "slide-conveying" mode, with the granular mass remaining permanently in contact with the trough walls. We present a detailed analysis of the mechanics of transport, based on a rigid-slab model for the granular mass with frictional (Coulomb) slip at the upper and lower walls. The form of the vibration cycle plays a crucial role, and the optimal conveying cycle is not the commonly assumed rectilinear sinusoidal motion. The conveying efficiency for the novel slide conveyor will be presented for several simple vibration cycles, including one believed to represent the theoretical optimum