Comparison of numerical simulations and birefringence measurements in viscoelastic flow between eccentric rotating cylinders

Abstract

Finite‐element predictions of steady, two‐dimensional viscoelastic flow based on the elastic‐viscous split stress formulation of Rajagopalan et al. [Rajagopalan, D., R. C. Armstrong, and R. A. Brown, ‘‘Finite Element Methods for Calculation of Steady, Viscoelastic Flow Using Constitutive Equations with a Newtonian Viscosity,’’ J. Non‐Newt. Fluid Mech. 36, 159–192 (1990)] are compared to birefringence measurements of stress for flow between eccentric rotating cylinders of a solution of polystyrene in tricresyl phosphate. Steady and small‐amplitude oscillatory shearing measurements are used to characterize the shear flow rheology of the fluid, and a four‐mode Giesekus model with a Newtonian solvent viscosity is fit to the rheological data. Comparison of the stress fields measured by flow‐induced birefringence in the one‐dimensional flow between concentric cylinders to the mechanically measured viscometric data show that the optical data compare reasonably well with the mechanical data. Comparison of optical...