An improved approach for aerodynamic optimization considering WIG effect and height static stability

To address the issue of inadequate height static stability of the airfoil under ground-effects, an aerodynamic optimization was conducted on the NACA4412 airfoil, targeting static height stability and adhering to a lift to-drag ratio constraint. This article adopted the class function/shape function transformation (CST) method to parameterize the airfoil and reduced the number of design variables by using a layered dimensionality reduction method. Firstly, the proper orthogonal decomposition (POD) was used to decrease the dimensionality of CST weight coefficients. Subsequently, the extracted modes were subjected to sensitivity analysis, and the final design variables were selected from those with a higher sensitivity. Combined with surrogate model, a data-driven design platform for airfoil in ground-effect aerodynamic optimization was established. The camber line of the optimized airfoil exhibits a wavy pattern that resembles S-curve. The optimization of the airfoil resulted in a forward shift the locations of the aerodynamic center of altitude and a backward shift in the locations of the aerodynamic center of pitch. This improvement increased the static height stability by 16.38%, with the change range of the lift-to-drag ratio is only 0.2425%, meeting the constraint requirements. The method has certain significance for the optimization of airfoils in ground effect area.