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Drag force in viscoelastic fluids

Elan Grossman, Basil Soofi, Ekapop Pairam and Alberto Fernandez-Nieves

These experiments are motivated by results in the Group of Dan Goldman (GaTech) with granular media. Among other things, our colleagues found that at a certain packing fraction, the drag exerted by sand on a bar as it displaced at constant speed exhibits oscillations related to formation of slip planes. Our goal is to see whether there is an analog to this behavior in colloidal microgel suspensions, which are an example of a viscoelastic fluid.


Figures 1 and 2 display our set-up. The brass par is connected to the linear actuator that moves across the stage at a constant velocity. The drag force is measure by a strain gauge placed on the bar. The bending of the bar due to the drag force is measured as a voltage and converted into a force.

We are currently calibrating the system and removing possible sources or error (such as noise). The movie below demonstrates a typical run (1 mm/s for 1 cm in water)

Contact Information:
Elan Grossman
Office: Boggs Building, Room B-54
Email address: egrossman3 [at] gatech.edu
Phone: 770-595-8339

Soft Condensed Matter Laboratory, School of Physics, Georgia Institute of Technology
770 State Street NW, Atlanta, GA, 30332-0430, USA
Phone: 404-385-3667 Fax: 404-894-9958
alberto.fernandez [at] physics.gatech.edu