A Constrainted Design Approach for NLF Airfoils by Coupling Inverse Design and Optimal Techniques
Lichi Deng, Yan Wu Gao, Z. D. Qiao, Jiachun Li, Song Fu · AIP conference proceedings · 2011
In present paper, a design method for natural laminar flow (NLF) airfoils with a substantial amount of natural laminar flow on both surfaces by coupling inverse design method and optimal technique is developed. The N‐factor method is used to design the target pressure distributions before pressure recovery region with desired transition locations while maintaining aerodynamics constraints. The pressure in recovery region is designed according to Stratford separation criteria to prevent the laminar separation. In order to improve the off‐design performance in inverse design, a multi‐point inverse design is performed. An optimal technique based on response surface methodology (RSM) is used to calculate the target airfoil shapes according to the designed target pressure distributions. The set of design points is selected to satisfy the D‐optimality and the reduced quadratic polynomial RS models without the 2nd‐order cross items are constructed to reduce the computational cost. The design cases indicated that by the coupling‐method developed in present paper, the inverse design method can be used in multi‐point design to improve the off‐design performance and the airfoils designed have the desired transition locations and maintain the aerodynamics constraints while the thickness constraint is difficult to meet in this design procedure.