Complex Fluids’ behavior of flow depends on driving, unlike Newtonian Fluids. Typically complex fluids show shear thinning or shear thickening behavior. In the latter, the viscosity increases with strain rate, whereas the behavior is opposite for shear-thinning fluids. In dense shear-thickening suspensions, this fluid can show an abrupt or discontinuous jump in viscosity called discontinuous shear thickening (DST).
There has been extensive research in recent years regarding the mechanism of DST, and there is a growing consensus in the community that frictional contacts are responsible for DST. We try to explain this phenomenon by constructing a statistical mechanics model on the vertices of force tiles constructed from the forces between particles in the hydrodynamic simulations that undergoes DST and extracting the contributions coming from the typically large frictional forces. The basis of our statistical mechanics approach is constraint satisfaction rather than free-energy minimization for a given interaction potential. These suspensions show DST by transitioning from lubricated to solid on solid frictional contacts under external stress. Also, doing statistical mechanics in force tiles is a neat way of capturing these changes in the pair-wise forces across the DST transition.
The construction of force tiles satisfies the constraint of force and torque balance on each grain, and along with these the Coulomb criterion on the frictional forces can lead to nontrivial correlations in the distribution of vertices of force tiles representing the collection of steady-state configurations belonging to the hydrodynamic simulations. These constraints are difficult to impose, and we assume that an apriori probability distribution derived from a pair-wise potential will model the correlations in the vertices of force tiles satisfying all these constraints and as a result, the system of vertices of force tiles will behave as an interacting gas. In this thesis, we establish the validity of this hypothesis.
|Commitee:||Hagan, Michael, Morris, Jeffrey|
|School Location:||United States -- Massachusetts|
|Source:||DAI-B 81/4(E), Dissertation Abstracts International|
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