Particle Pressure : A Bridge from Osmosis to Granular Dilatancy
Abstract
The normal stress exerted by particles in a sheared suspension is measured by analogy with a method used to measure osmotic pressure in solutions. Particles in a liquid of equal density are confined by a fine screen to a gap between two vertical concentric cylinders, the inner of which rotates. Pressure in the liquid is sensed either by a manometer or by a pressure transducer across the screen. The particles are large enough so that Brownian motion and equilibrium osmotic pressure are vanishingly small. The measured pressure yields the shear-induced particle pressure Π, which is the nonequilibrium continuation of equilibrium osmotic pressure. For volume fractions 0.3 ≤ φ ≤ 0.5, Π is strongly dependent on φ, and linear in shear rate. Comparisons of the measured particle pressure with modeling, experimental derivations, and simulation show good agreement.
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