Non-Newtonian shear-thinning flows past a flat plate

The present work attempts to characterize the flow of shear-thinning power-law fluids past a flat plate as the angle of attack is varied. The effects of Reynolds number, shear-thinning characteristics and angles of attack on drag and lift of the flat plate were investigated, both experimentally and numerically. Carbopol 940 solutions of various strengths were used to approximate purely viscous shear-thinning non-Newtonian fluids for the experiments. An important finding is that at small 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 form drag is dominant, shear-thinning results in drag augmentation. This is consistent with the trend shown in the present study that lift increases as shear-thinning increases. It is demonstrated that a simple linear model developed for Newtonian creeping flow can be used to estimate the effect of angle on drag given both the drag coefficients corresponding to normal and tangential flow to the plate.