NON-NEWTONIAN SHEAR-THINNING FLOWS PAST A FLAT-PLATE

The present work attempts to characterize the flow of shear-thinning p ower-law fluids past a flat plate as the angle of attack is varied. Th e effects of Reynolds number, shear-thinning characteristics and angle s of attack on drag and lift of the flat plate were investigated, both experimentally and numerically. Carbopol 940 solutions of various str engths were used to approximate purely viscous shear-thinning non-Newt onian fluids for the experiments. An important finding is that at smal l angles of attack when the wall shear forms the dominant contribution to the drag, the non-Newtonian shear-thinning property leads to drag reduction, whereas for large angles of attack, when pressure-induced f orm drag is dominant, shear-thinning results in drag augmentation. Thi s is consistent with the trend shown in the present study that lift in creases as shear-thinning increases. It is demonstrated that a simple linear model developed for Newtonian creeping flow can be used to esti mate the effect of angle on drag given both the drag coefficients corr esponding to normal and tangential flow to the plate.