Lift Maximization with Uncertainties on Angle of Attack for High Lift Devices Optimization

In this report, we address aerodynamic shape optimization problems including uncertain operating conditions. After a review of robust control theory and the possible approaches to take into uncertainty, we propose to use Taguchi robust design methods in order to overcome single point design problems in Aerodynamics. The latter techniques produce solutions that perform well for the selected design point but have poor off-design performance. Under the conduct of Taguchi concept, a design with uncertainties is converted into an optimization problem with two objectives which are mean performance and its variance, so that the solutions are as less insensitive to the uncertainty of the input parameters as possible. Furthermore, the Multi-Criterion Evolutionary Algorithms (MCEAs) are used to capture a set of compromised solutions (Pareto front) between these two objectives. The flow field is analyzed by Navier-Stokes computation. In order to reduce the number of expensive evaluations of fitness function, Response Surface Modelling (RSM) is employed to estimate fitness value using the polynomial approximate model. The proposed approach is applied to the robust optimization of the 2D high lift devices of a business aircraft, by maximizing the mean and minimizing the variance of the lift coefficients with uncertain free-stream angle of attack at landing and takeoff flight conditions respectively