Aerodynamic characteristics and lift enhancement mechanism of mini-TED in transonic flow

By means of solving two dimensional and compressible Navier-Stokes equations, the transonic flow-field characteristics of NACA0012 airfoil equipped with mini trailing edge lift enhancement device (mini-TED) was investigated, and the influences of geometrical parameters on the vortices and aerodynamic characteristics of airfoil were analyzed and compared with the Gurney flap(GF). The two orthorhombic geometry detailed parameters were defined as chord-wise length and effective height to describe the geometric features. Only the chord-wise length changed at the same angle of attack, although the trailing edge vortices varied greatly, the aerodynamic characteristics of airfoil had little change. On the other hand, the trailing edge vortices and the aerodynamic characteristics of airfoil varied significantly with the effective height changed, and the aerodynamic characteristics were very close to the GF in the same condition of effective height. Result shows that the effective height plays a dominant role in affecting the aerodynamic characteristics of airfoil. Rather than the microstructure and shape, the size of the vortices is the main factor influencing the flow field of airfoil as this is mainly decided by the effective height. With the mini-TED, compared with the original airfoil, the shock wave on the upper surface of the airfoil moves backward and the strength of the lower shock wave is weakened, so the pressure coefficient of airfoil surface changes. With the increasing effective height, the induced vortices scope becomes larger, enhancing the drainage effect and increasing the lift coefficient, drag coefficient and nose-down pitching moment coefficient. The lift-drag ratio is improved at the same angle of attack as well.