Year: 2026
Type: preprint
Abstract: An exploration is presented of two-dimensional, circular Couette flow of an elasto-viscoplastic fluid described by Saramito's (Bingham) constitutive law. Axisymmetrical base states are constructed. As has been noted previously, such states are not unique, with stresses over any plugs depending on the initial polymer stress, and the shear rate and stress may jump discontinuously across the yield surfaces. We show that base states with continuous stress profiles are linearly unstable at zero Reynolds number when they contain regions with relatively low shear rate. Unstable modes become stronger and localized to the yield surfaces as the azimuthal wavenumber increases. We report numerical simulations exploring the nonlinear dynamics of the instability. The linear unstable modes saturate at finite amplitude to create spatio-temporally complicated states. Polymer stress diffusion is added to ease these numerical simulations, eliminating normal-stress discontinuities and instability at the shortest wavelengths. Instability and transition to complex dynamics occur whenever the base flow contains regions with relatively low shear rate.
Source: arXiv (Cornell University)
Institutions: University of British Columbia, University of Cambridge
Language: English
Subfield: Fluid Flow and Transfer Processes
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221172017