Lift characteristics of an airfoil at low Reynolds numbers for Newtonian and shear-thinning Carreau fluids

Abstract

In the present study, we have numerically investigated Carreau and Newtonian fluid flow over a stationary National Advisory Committee for Aeronautics 0012 airfoil using a sharp interface immersed boundary method. We have explained the mean lift behavior and stall phenomena by identifying different vortex formation patterns over the airfoil surface for different angles of attack. We found that not all but some shear-thinning fluids avoid stall altogether at high angles of attack. It is observed that the lift behavior is strongly related to the frequency of vortex departure from the suction surface. We have correlated fluctuating energies with mean lift characteristics, which is one of the novelties of our work. We have also used time-averaged vorticity transport rate analysis to explain the effect of non-linear viscosity distribution in the departure of vortices at high angles of attack. It is observed that the apparent viscosity dominates the transport of vorticity, and the effect of shear straining is negligible at high angles of attack.