Fully developed turbulent flow of non–Newtonian liquids through a square duct

Abstract

The results are reported of an experimental investigation of fully developed turbulent flow through a square duct of water (as a control) and of two polymers, an aqueous solution of 0.1% carboxymethylcellulose + 0.1% Keltrol TF, a xanthan gum (CMC/XG) and a 0.125% aqueous solution of a polyacrylamide, Separan AP 273 (PAA). The more elastic rheology of PAA leads to drag–reduction levels up to 77%, compared with 65% for CMC/XG. There are also substantial reductions in the levels and changes in the spatial distribution of the transverse turbulence intensities and the Reynolds shear stress, again dependent on the degree of viscoelasticity of the working fluid. Concomitant changes are evident in the secondary flow, which depends upon second derivatives of the Reynolds stresses, and also in the primary axial flow due to the redistribution of axial momentum by the secondary flow.