Fully developed turbulent flow of non-Newtonian liquids through a square duct
Proceedings of the Royal Society A
The results are reported of an experimental investigation of fully developed turbulent flow through an 80mm x 80mm duct of water and of two shear-thinning polymers, an aqueous solution of 0.1% carboxymethylcellulose + 0.1% xanthan gum (CMC/XG) and a 0.125% aqueous solution of polyacrylamide (PAA). The more elastic PAA leads to drag-reduction levels up to 77% compared with 65% for CMC/XG. It is well established (e.g. Nikuradse (1930), Melling and Whitelaw (1976) that contours of mean axial
... of mean axial velocity are a good indicator of the strength of the turbulence-induced secondary flow. We find that for water the contours away from the walls and the channel centre bulge towards the corners as a consequence of the transport of fluid with high axial momentum into regions where the momentum would otherwise be low. For CMC/XG this tendency is much reduced and absent for PAA. B Gampert, A Rensch, Polymer concentration and near-wall turbulence structure of channel flow of polymer solutions, ASME FED-237, 1996 Fluids Eng Div Conf, 2 (1996 129-136. J P Hartnett, M Kostic, Turbulent friction factor correlations for power law fluids in circular and non-circular channels, Int Comm heat Mass Transfer, 17 (1990) 59. J P Hartnett, E Y Kwack, B K Rao, Hydrodynamic behaviour of non-Newtonian fluids in a square duct, J Rheology 30 (S) (1986) S45. J P Hartnett, B K Rao. Heat transfer and pressure drop for purely viscous non-Newtonian fluids in turbulent flow through rectangular passages, Wärme Stoffübertrag. 21 (1987) 261. M Kostic, On turbulent drag and heat transfer reduction phenomena and laminar heat transfer enhancement in non-circular duct flow of certain non-Newtonian fluids, Int J Heat Mass Transfer 37, Suppl 1 (1994) 133. M Kostic, J P Hartnett, Heat transfer performance of aqueous polyacrylamide solutions in turbulent flow through a rectangular channel, Int Comm Heat Mass Transfer. 12 (1985) 483. W Kozicki, C H Chou, C Tiu, Non-Newtonian flow in ducts of arbitrary cross-sectional shape, Chem Eng Sci 21 (1966) 665. W Kozicki, C Tiu, Improved parametric characterization of flow geometries, Can J Chem Eng 49 (1971) 562. S E Logan, Laser velocity measurements of Reynolds stress and turbulence in dilute polymer solutions, AIAA J 10 (1972) 962-964. A Melling, J H Whitelaw, Turbulent flow in a rectangular duct, J Fluid Mech 78 (1976) 289. J Nikuradse, Turbulente Strömung in nichtkreisförmigen Rohren, Ing.-Arch. 1 (1930) 306. J T Park, R J Mannheimer, T A Grimley, T B Morrow, Pipe flow measurements of a transparent non-Newtonian slurry, J Fluids Eng, 111 (1989) 331.