Experimental characterization of Newtonian and non-Newtonian fluid flows in corrugated channels

The main goal of this experimental study is to determine the friction mecha nisms which govern transfer properties on corrugated walls with large ampli tude. We have considered Newtonian and non-Newtonian pseudoplastic fluids f or the laminar or turbulent flow regimes. Experiments rely on the use of tw o different techniques: the electrochemical method used for the measurement of the wall shear rate S and the laser velocimetry for the determination o f the axial velocity profiles. Our local observations for a wavy two-dimens ional channel especially concern the evolution of mean and fluctuating vari ables as a function of the flow rate or of a generalized Reynolds number. S ome new results are presented for the different flow regimes and their spec ificities. The influence of the pseudoplasticity character on the wall tran sfer, on the shape and position of recirculating zones downward the undulat ions has been pointed out. (C) 1999 Elsevier Science Ltd. All rights reserv ed.