Drag force in a yieldstress fluid
Abstract
We measure the drag force exerted on a sphere being pulled at constant speed through a suspension of Bentonite clay in water. We find that the drag force is independent of velocity over the range of velocities studied. The drag force does, however, depend on the time after mixing of the suspension due to changes in the properties of the material as it ages. When the ball starts moving from rest, the force approaches its steady state value with a single exponential time constant at higher speeds, but with two distinct time constants at low speeds. This indicates that the response of the material to shear involves at least two processes.
 Publication:

APS Division of Fluid Dynamics Meeting Abstracts
 Pub Date:
 November 2003
 Bibcode:
 2003APS..DFD.KK001C