Research On Unsteady Aerodynamic Characteristics Of An Aircraft Model With Leading-Edge Extension At High Angle Of Attack

Research on the dynamic aerodynamic characteristics of aircraft with Leading-Edge Extension at highangle of attack provides important basis for design optimization of new aircraft. Unsteady force andmoment are couple with movement during the process of high angle of attack maneuver of the aircraftwith Leading-Edge extension. Aerodynamic parameters present non-linear and unsteadycharacteristics. One of the characteristic phenomenon is the hysteresis loop of the dynamic force andmoment. A model aircraft with Leading-Edge extension is adopted in this thesis. A series of dynamicwind tunnel test of rolling movement, yaw motion and the coupled motion are performed in the attackangle of25.87°and35.15°. Firstly, the dynamic force test of rolling, yaw and the coupled motion isperformed in the both attack angle. The graphs of rolling moment coefficient and yaw momentcoefficient versus sideslip angle were obtained under the different frequency in different movements.The hysteresis loop of rolling coefficient and yaw coefficient is obvious, which indicate that thehysteresis effect is remarkable. The hysteresis loop becomes big as frequency increases. All graph ofmoment coefficient of coupled motion of rolling and yaw shows no hysteresis loop, which indicate nohysteresis effect. In the next, a span-wise dynamic pressure distribution measure is performed indifferent aspect ratio positions in the same condition and law of motion. The experiment result showsthat the pressure peak is obvious in the rolling and yaw. The asymmetry of pressure increases as themovement frequency increases. The hysteresis effect of pressure distribution is obvious, which causethe moment hysteresis in the corresponding movement. There is no peak in the pressure distribution ofcoupled motion, overall pressure is lower. There is no hysteresis effect is showed as well as thecorresponding moment. Finally, A PIV experiment is performed in the same attack angle and law ofmotion. The experiment result shows that the flow-field response of the model in the same attitude butin different distance of travel is different. This difference affects the pressure distribution of wingsurface directly, hence cause pressure distribution hysteresis. The flow-field response to differentdistance of travel is minor in the coupled motion, hence the pressure distribution and moment show nohysteresis effect.