Title: Mobility Condition for a Particle on a Rough Surface in a Fluid Flow

Author (Poster): David Scheff, Clark University

Abstract:

We advance a quantitative description of the critical shear rate needed to dislodge a spherical particle resting on a surface with a model asperity in laminar and turbulent fluid flows. We have built a cone-plate experimental apparatus which enables measurement of the critical shear rate over a wide range of particle Reynolds number Re from 10^-3 to 1.5 x 10^3. The data is found to be consistent with the condition given by torque balance, which differs from force balance because of the torque due to drag about the particle center. The data for Re less than 0.5 is in good agreement with analytical calculations of the drag and lift coefficients in the Re approaches 0 limit. For higher Re, where analytical results are unavailable, the hydrodynamic coefficients are found to approach a constant for Re less than 1000. We show that a linear combination of the hydrodynamic coefficients found in the viscous and inertial limits can describe the overall critical shear rate as a function of the particle and fluid properties.