Relaxation of Dense Suspension
Name
griese-agriese-sm-meche-2021-thesis.pdf
Description
Thesis PDF
Size
2.44 MB
Format
Adobe PDF
Checksum (MD5)
32962b1f5b10b88d52dcd1d9d7a88b8d
Author(s)
Griese, Andrew Herman
Advisor(s)
Bischofberger, Irmgard
Date Issued
June 2021
Publisher
Massachusetts Institute of Technology
Abstract
Dense suspensions exhibit complex rheological behavior by behaving liquid-like at low shear stresses and solid-like at high shear stresses. The microscopic interactions between individual particles create non-Newtonian macroscopic behaviors by transitioning from hydrodynamic interactions to frictional contacts. As the particles are forced into frictional contact, the suspension’s viscosity discontinuously increases with respect to the shear rate, leading to solid-like characteristics. While much research has gone into how a suspension enters this solid-like state, little is known about how the suspension relaxes out of this stressed rheological state. To understand the relaxation behavior and its underlying physical mechanism, we investigate the relaxation of water-cornstarch mixtures at different cornstarch mass fractions. The relaxation of these cornstarch suspensions is explored by measuring the stress decay upon flow cessation with a rheometer and a texture analyzer, and by capturing the spreading dynamics of suspension drops upon the cessation of vibrations with a permanent magnet shaker. We show that the dense suspensions relax with two distinct timescales, and that both of these timescales are linearly dependent on the suspension viscosity in the stressed state.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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