LOCAL FLOW STRUCTURE FOR NON-NEWTONIAN FLUIDS IN A PERIODICALLY CORRUGATED WALL CHANNEL

Experiments were carried out to characterize the local shear flow insi de a periodically corrugated wall channel by use of electrochemical me thod giving the wall shear rate S and laser-Doppler velocimetry (LDV) for the axial velocity profiles. Both Newtonian fluids and shear-thinn ing viscous fluids (carboxymethyl-cellulose sodium salt (CMC) additive ) are considered, flowing in a range of Reynolds numbers and generaliz ed Reynolds numbers for non-Newtonian fluids determining the following regimes: laminar, transitional and low-Reynolds-number turbulent. Lam inar flow, steady motion with a recirculating zone, transition to turb ulence with unsteady vortex and three-dimensional instabilities with r educing by the onset of a developed turbulence have been detected.