Fluid dynamics of dilatant fluid

TL;DR

This paper develops a fluid dynamics model for dilatant fluids, capturing their shear thickening behavior, hysteresis, and oscillatory flow, supported by numerical simulations.

Contribution

Introduces a phenomenological model with a state variable to describe dilatant fluid behaviors like shear thickening and oscillations.

Findings

Model reproduces shear thickening and hysteresis.

Predicts shear thickening oscillations in flow.

Numerical simulations confirm theoretical predictions.

Abstract

Dense mixture of granules and liquid often shows a sever shear thickening and is called a dilatant fluid. We construct a fluid dynamics model for the dilatant fluid by introducing a phenomenological state variable for a local state of dispersed particles. With simple assumptions for an equation of the state variable, we demonstrate that the model can describe basic features of the dilatant fluid such as the stress-shear rate curve that represents discontinuous severe shear thickening, hysteresis upon changing shear rate, instantaneous hardening upon external impact. Analysis of the model reveals that the shear thickening fluid shows an instability in a shear flow for some regime and exhibits {\it the shear thickening oscillation}, i.e. the oscillatory shear flow alternating between the thickened and the relaxed states. Results of numerical simulations are presented for one and two-dimensional systems.