Examining the Aerodynamic Drag and Lift Characteristics of a Newly Developed Elliptical-Bladed Savonius Rotor

The elliptical-bladed Savonius wind turbine rotor has become a subject of interest because of its better energy capturing capability. Hitherto, the basic parameters of this rotor such as overlap ratio, aspect ratio, and number of blades have been studied and optimized numerically. Most of these studies estimated the torque and power coefficients (CT and CP) at given flow conditions. However, the two important aerodynamic forces, viz., the lift and the drag, acting on the elliptical-bladed rotor have not been studied. This calls for a deeper investigation into the effect of these forces on the rotor performance to arrive at a suitable design configuration. In view of this, at the outset, two-dimensional (2D) unsteady simulations are conducted to find the instantaneous lift and drag forces acting on an elliptical-bladed rotor at a Reynolds number (Re) = 0.892 x 10(5). The shear stress transport (SST) k-omega turbulence model is used for solving the unsteady Reynolds averaged Navier-Stokes equations. The three-dimensional (3D) unsteady simulations are then performed which are then followed by the wind tunnel experiments. The drag and lift coefficients (C-D and C-L) are analyzed for 0-360 deg rotation of rotor with an increment of 1 deg. The total pressure, velocity magnitude, and turbulence intensity contours are obtained at various angles of rotor rotation. For the elliptical-bladed rotor, the average C-D, C-L, and C-P, from 3D simulation, are found to be 1.31, 0.48, and 0.26, respectively. The average C-P for the 2D elliptical profile is found to be 0.34, whereas the wind tunnel experiments demonstrate C-P to be 0.19.