Enhancing the performance of airfoils can help in improving the performance of many devices such as Darrieus Vertical Axis Wind Turbines (VAWTs.) Several methods have been proposed in the literature to control the flow over airfoils. These included using Gurney flap, using leading edge flap, slotted airfoils as well as others. The Gurney flap is a fixed flap installed normal to the airfoil surface at its trailing edge. The length of the Gurney flap, its position and its orientation are important design parameters investigated in the present work. The effect of Gurney flap parameters on the lift and drag forces as well as the lift to drag ratio (glide ratio) are assessed for different angles of attack. The present study was performed using Computational Fluid Dynamics (CFD) technique. The computational model was validated and mesh sensitivity tests were carried out to ensure accurate model results. The SST k-ω model of turbulence was used to close the Reynolds averaged Navier Stokes equations. The results showed that locating the Gurney flap on the top orientation of the airfoil has bad effect on lift and drag, while locating it on the lower side improved lift to drag ratio. Based on the significance increase of the glide ratio of airfoil with Gurney flap compared to the baseline airfoil, the best length of Gurney flap is 2% of chord length and the best position of Gurney flap to be added is to the airfoil trailing edge while the best orientation of the Gurney flap is down aligned with the airfoil pressure side. The lift coefficient is increased significantly by an average of 30%, also the drag coefficient is slightly increased by an average of 15% compared to the lift and drag generated by the baseline airfoil.