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

Abstract

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.