Abstract:
In order to improve the longitudinal stalling characteristics of landing configuration, a certain large civil transport aircraft was investigated by computational mothed based on CFD tools and grid generation technique. The computational method was validated by wind tunnel results. The whole aircraft was divided in seven parts, which are the fuselage, inboard wing, middle wing, outboard wing, wingtip, nacelle, and horizontal tail. The results show that the contribution of the inboard and middle wing is negative to the inflexion of pitch moment curve. The stalling characteristics can be improved by worsening the aerodynamic characteristics of the inboard and middle wing, but this worsening procedure decreases the maximum lift coefficient and stalling angle of attack. At high angle of attack and low coming flow speed, there are massive separations in upper surface of the wingtip. The contribution of these separations is positive to the inflexion of pitch moment curve. The leading edge of modified wingtip may induce strong vortex, which can restrain the production and development of massive separation, therefore, the longitudinal stalling characteristics are improved. However, the cruise induced drag is increased due to the modification. A balanced choice needs to be executed for low and high incoming flow speed. The contribution of the horizontal tail is positive to the longitudinal stalling characteristics. The influence of the root vortex of inboard flap is extremely significant on local flow around the horizontal tail. By cowling modification, this influence can be restrained, and the angle of attack increases by 4° for the inflexion of pitch moment curve.