Optimization Methods For Supercritical Natural Laminar Airfoils

Laminar flow technology research is a research subject that has drawn much attention in recent years because of its great potential in aircraft design,especially in civil aircraft drag reduction technology.Aiming at the optimization design method of transonic natural laminar flow,a computational fluid dynamics(CFD)calculation program is established.This method integrates the method of solving RANS equations with method of e~N transition prediction,the automatic generation method of high-quality grids,the parameterization method applicable to supercritical natural laminar airfoils,and the combination of BOBYQA(Bound Optimization BY Quadratic Approximation)with high efficiency without derivative information optimization iterative algorithm.1)A numerical simulation platform is automatically determining the position of airfoil boundary layer transition.By numerical simulation of several classic airfoil examples and automatic grid generation method,the reliability of the numerical method and the accuracy of e~N prediction method are verified,which can provide a reliable,high Accuracy of the CFD calculation program.2)Three parameterization methods of CST,PARSEC and iCST are studied.By comparing the fitting errors of the three airfoils,from this we can see most of PARSEC parametric modeling results do not meet the error criteria,and the CST and iCST parameterization methods have good fitting accuracy,which is feasible for the following optimization design.3)The optimization design method of supercritical natural laminar airfoil is verified,it is based on RAE2822 supercritical airfoil with drag reducing as the goal.The optimized airfoil enlarges the range of the gradient along the airfoil surface,reduces the friction drag,increases the drag ratio,and the airfoil has the transonic aerodynamic performance and meets the characteristics of the natural laminar airfoil.The influence of lift coefficient and Mach number on the airfoil optimization of natural laminar flow in the supercritical fluid is studied.With the increase of design lift coefficient,the area of laminar flow on the upper airfoil decreases with the airfoil optimization,and the position of the transition is shifted forward.The Mach number of the optimal result becomes smaller and the position of the transition point of the lower surface moves backward.