Control of Aerodynamic Characteristics of Airfoils and Wing Systems in Subsonic Flow

The results of experimental investigations of control of composite separation-vortical flows and aerodynamic characteristics of lifting units ((i) symmetric and asymmetric airfoils, (ii) wings, (iii) wing systems) at low and high angles of attack are discussed. The control was performed by means of the spanwise baffles mounted on the leeward side of airfoils and wings, and also on the base of useful interaction of vortical structures of a wing system. The investigations are carried out in three subsonic wind tunnels of MAI at free-stream velocities V∞ = 30.82–47 m/sec and Reynolds numbers Re_rl = 0.86.10⁶–2.2.10⁶ based on the reference length rl =1 m. The tests of the airfoil sections are performed in the range of angles of attack from 0° up to 26°. The wings and the wing systems were tested at the angles of attack from −4° to +45°. It was found, that the mounted baffles result in formation of the attached circulating regions to airfoil with dropping pressure and the inspected flow separation. These phenomena promote the increase of the airfoil lift and can be used as effective means of control of its aerodynamic characteristics. It was shown, that the installation of two spanwise baffles on the consoles allowed organizing vortex trapping on the upper surface of a wing. These high-lift devices permit to increase the critical angle of attack of such wing, its lift and also to reduce wing drag at high angles of attack. It is established the possibility to use interaction effects of vortical structures in wing systems for increase of lifting properties at high angles of attack and reduction of pressure oscillations on streamlined surfaces. These effects are the important factor for lowering of acoustic loads on airframe units and downturn of a level of aircraft buffering.