Study Of Multi-level Response Surface Optimization For The Winglet

After the installation of winglets, the lift of aircraft can be increased, while drag and fuel are reduced, leading to an increase of range and load, which can bring us great economic benefits. So far, it becomes more and more popular to amount winglets on the large transport aircraft over the world. Compared with the winglet-only shape optimization, the wing-and-winglet integrated design is more conducive to improve the aerodynamic performance of aircraft, and has a wider range of engineering application prospects. The wing-and-winglet intergrated design technology has been used on most domestic and foreign advanced aircrafts, such as Boeing747-400, Boeing787, Airbus330, Airbus340 and ARJ21.The study in this paper is focous on the installation of winglets for a certain type of amphibious aircraft.In order to improve the efficiency and accuracy of the calculation ,an optimization method based on multi-level response surfaces is proposed for the aerodynamic shape design. The basic idea is as follows. First, use a screening test Plackett-Burman design to screen and classify the design parameters on the basis of their respective effect to the objective function. After that, use steepest ascent method to obtain design center point of significant factors above 95% probability level. And finally obtain optimum design parameters by using Box-Behnken design and multi-level response surface optimization together with sequential quadratic programming method. In this way, two examples are caculated respectively. One is winglet-only shape optimization, and the other is wing-and-winglet intergrated design. The results of the examples indicate that the method has relatively small caculation but high accuracy and reliability, and has some practical value in engineering application.