SC18   James Swan Memorial Symposium 


Suspensions and Colloids


Thixotropy as a dynamic regularizer for elasto-visco-plasticity


October 10, 2022 (Monday) 5:45


Track 1 / Sheraton 4

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  1. Swan, James W. (Massachusetts Institute of Technology, Chemical Engineering)
  2. Matteucci, Nicholas J. (Massachusetts Institute of Technology, Chemical Engineering)

(in printed abstract book)
James W. Swan and Nicholas J. Matteucci
Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139


Matteucci, Nicholas J.


theoretical methods; computational methods; colloids; gels; suspensions


Thixotropic yield stress materials are found in numerous suspension and polymer mixtures of industrial and commercial interest. While numerous theoretical treatments of these materials exist, many rely on discontinuous functions to describe the yielding transition. In this presentation, we study thixotropic yield stress fluids, focusing on how thixotropy regularizes the yiedling transition of visco-plastic and elasto-visco-plastic materials. We propose simple models for thixotropic fluids, which are continuously differentiable with respect to all variables and parameters. In the limit that the thixotropic response of the fluid is asymptotically fast, these models transform into well-known models for visco-plastic and elasto-visco-plastic materials. A new dimensionless group is named in this work: the Fredrickson number, which is the ratio of the dynamic yield stress of the fluid to the viscous stress generated by shear with a shear rate equal to the inverse of a thixotropic relaxation time. This group depends only on the properties of the thixotropic fluid and is an important control parameter in conditions where fluid motion is driven by an applied stress. The responses of the proposed thixo-visco-plastic and thixo-elasto-visco-plastic models under different flow scenarios, such as oscillatory shear and pressure-driven flow, will be discussed in detail.