Turbulent flow of a viscoelastic shear-thinning liquid through a plane sudden expansion of modest aspect ratio

An experimental investigation is reported of turbulent flow of a 0.125% polyacrylamide (PAA) solution, a shear-thinning and viscoelastic liquid, through a plane sudden expansion of expansion ratio R = D/d = 4 and aspect ratio A = w/h = 5.33. A Newtonian fluid flow through the same geometry has been reported previously [Phys. Fluids 14 (2002) 3641] and limited results from that study are included here for comparative purposes. It is well known, for Newtonian fluids at least, that plane sudden expansions with R greater than 1.5 produce asymmetric flows. For the viscoelastic fluid flow, this asymmetry was initially (x/d < 6) reduced but not eliminated and the flow found to be highly three dimensional and complex. Results are reported at three spanwise locations to highlight this three dimensionality. (C) 2003 Elsevier Science B.V. All rights reserved.