They examined the effect of the sinusoidal edge wavelength on drag coefficient, vortex shedding, and frequency.
( 2008) conducted a numerical study on the sinusoidal edge effect in a flow stopping airfoil-like body with a thick edge to determine how it affected the aerodynamic characteristics of this body. Using a moderate cavity not only improved the drag-reducing performance of the splitter plate, but also limited the unsteady vortex shedding.Ĭai et al.
Although a base cavity reduced drag by up to 25%, it also introduced drastic fluctuations in lift. Their results showed that using the splitter plates could reduce drag by up to 50%.
To reduce drag, they implemented two splitter plates as well as open and moderate cavities. They used a pyramidal balance for the measurement of the lift and drag at Davis aeronautical wind tunnel. The wind tunnel results are compared with computational predictions obtained in OVERFLOW, a Reynolds-averaged Navier–Stokes solver using structured overset grids.īaker and Dam ( 2008) numerically and experimentally studied the FB-3500-1750 airfoil with blunt trailing-edge and used certain instruments to reduce the drag and increase the lift for improving the performance of this airfoil.
Both free and fixed transition conditions were studied. In the experimental part, lift and drag force measurements were carried out in Davis aeronautical wind tunnel at Reynolds numbers of 333,000 and 666,000. ( 2010) numerically and experimentally studied the characteristics of UCD-38-095 airfoil with blunt trailing edge. ( 2007), and Gerontakos and Lee ( 2008) studied experimentally the flow characteristics of an airfoil to understand the vortex shedding mechanism.Ĭooperman et al. ( 2015) studied numerically, and Bourgoyne et al. Mathey ( 2008), Heskestad and Olberts ( 1960), and Zhang et al. Improving the aerodynamic performance of airfoils with thickened edges would require certain drag-reducing instruments (Javarashkian and Lotfi 2008). Thus, the recovered pressure can be partially transferred to the separation region produced by the airfoil. This positive pressure gradient can be somewhat reduced using a thickened edge. The gradual reduction of sharpness at the downstream of the maximum thickness section of an airfoil creates a strong positive pressure gradient at its low-pressure side, leading to an untimely flow separation. However, for certain applications (e.g., a wing in high attack angles), an airfoil with a thick trailing edge is required. In the conventional airfoils, the trailing edge ends to a sharp point. Graphical abstractĪirfoils with thickened edges are used in subsonic flow to resolve many of the problems encountered in the conventional airfoils. Furthermore, using cavity decreases the Strouhal number and vortex shedding frequency. Moreover, adding a cavity to the end of the thickened airfoil causes an increase in momentum and a further decrease in the wake behind the trailing edge that leads to a drag reduction in comparison with the thickened airfoil without cavity. The results show that cutting off the end of the airfoil decreases the wake region behind the airfoil, when separation occurs. Continuous measurement of unsteady flow velocity over the Riso airfoil with thick blunt trailing edge and base cavity is the most important innovation of this research.
Then, adding two parallel plates to the end of the new airfoil forms the desired cavity. The velocity field around the original airfoil and the new airfoil is measured by PIV technique and compared with each other. First, by cutting 30% chord length of the Riso airfoil, a thick blunt trialing-edge airfoil is generated. In this study, the effect of cutting the end of a thick airfoil and adding a cavity on its flow pattern is studied experimentally using PIV technique.