VISCOELASTIC FLOW PAST A CONFINED CYLINDER OF A POLYISOBUTYLENE SOLUTION

Viscoelastic constitutive equations are evaluated using the benchmark problem of the planar flow past a confined cylinder for a well-charact erized solution of 5%(w/w) polyisobutylene in tetradecane. The ratio o f channel height to cylinder diameter is equal to two. We compare fini te element simulations with point-wise measured velocities and stresse s obtained by means of laser Doppler anemometry and a flow-induced bir efringence technique, respectively. The Deborah number (De) ranges fro m 0.25 to 2.32. In the case of the geometry with a symmetrically confi ned cylinder, computations were made with a generalized Newtonian mode l and with both a single- and a four-mode Phan-Thien and Tanner (PTT) model. All model parameters were determined in simple shear flow. A si milar analysis is presented in case of an asymmetrically confined cyli nder (with De = 1.87). Impressively good agreement was found between t he predictions of the four-mode PTT model and the measured velocities and stresses. The agreement was even excellent in the geometry with th e asymmetrically confined cylinder. (C) 1995 Society of Rheology.