### Particle segregation in oscillating straining flows

**Marshall, J ***(Vermont)*

Thursday 08 January 2009, 14:25-14:50

Seminar Room 1, Newton Institute

#### Abstract

Numerical computations performed using a discrete-element method for both adhesive and non-adhesive particles indicate that particles placed in an oscillating straining flow will drift towards the nodal points of straining - a phenomenon that we refer to as oscillaing clustering. A theoretical prediction of this phenomenon is developed which yields the particle drift rate toward the straining nodal point, which is found to increase with increase in particle Strokes number up to a stability limit. The theory also predicts that in the presence of gravitational force, particles will exhibit a limit cycle behaviour in which they oscillate under the opposing downward gravitational drift and upward drift due to oscillating clustering. Computations are performed to demonstrate the effects of this phenomenon for particles in an oscillating box, for peristaltic pumping of a particulate suspension, and for a suspension flowing through a corrugated tube.

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