Response Surface Approximations for Aerodynamic Parameters in High Speed Civil Transport Optimization

Abstract

A procedure for generating and using polynomial approximations to the range or to the cruise drag components in terms of 29 design variables for a High Speed Civil Transport configuration design is presented. Response surface methodology is used to fit quadratic polynomials to data gathered from a series of numerical analyses of different aircraft designs. Several techniques are employed to minimize the number of required analyses and to maintain accuracy. Approximate analysis techniques are used to find regions of the design space where reasonable aircraft designs could occur and response surface models are built using higher fidelity analysis results of designs in this "reasonable" region. This is a means of using results from advanced CFD methods at the early design stage. Regression analysis and analysis of variance are used to reduce the number of polynomial terms in the response surface model functions. Optimization runs of the aircraft configuration are then carried out with the response surface models and compared to the previous optimization runs without the response surface models. It is shown that considerable reduction of the amount of numerical noise in optimization is achieved with response surface models and the convergence rate is improved. Careful attention was required to keep the accuracy of the models at an acceptable level.