## Modeling Thixotropic Yield Stress Fluids

**Faculty**: Kara Maki

**Summary:**

Rheology is the study of the deformation and flow of matter such as pastes, suspensions, slurries, or foods. One rheological effect that distinguishes a rheologically interesting fluid, i.e., a non-Newtonain fluid, from a conventional fluid, i.e., Newtonian fluid, is yield stress. Yield is the tendency for a complex fluid to flow as a liquid only above a nonzero critical shear stress. Put another way, a yield stress fluid can support its own weight to a certain extent. In thixotropic fluids, the yield stress is time dependent. These characteristics are exploited in both nature and engineering. For example, snails can climb on walls and ceilings because they excrete and crawl on a yield stress fluid. We investigate the yielding and unyielding dynamics of a simple model that captures features of a thixotropic yield stress fluid.

**Publications**:

- The dynamics of a viscoelastic liquid which displays thixotropic yield stress behavior, K. L. Maki and Y. Renardy, Submitted to the Journal of Non-Newtonian Fluid Mechanics.
- The dynamics of a simple model for a unified treatment of thixotropic yield stress fluids,
K. L. Maki and Y. Renardy,
*Journal of Non-Newtonian Fluid Mechanics*165 (2010), 1373-1385.

Collaborators:

Yuriko Renardy (Virginia Tech)