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.