Transonic Natural Laminar Flow Airfoil Design

Reducing the drag by the laminar flow design is an important measure to improve the economy of civil aircraft. It is the leading-edge technology of the current aviation. This paper mainly focuses on the method and application of natural transonic laminar flow airfoils optimization design.A optimization design method for transonic natural laminar flow airfoil has been proposed firstly. In this method, a CST parametric method is developed to parameterize the airfoil geometry and the coefficients of the part shape function are utilized as design variables. The aerodynamics of airfoils is calculated by high-fidelity CFD computation based on the k-ω SST + θtγ ?Re four equations turbulence model. Modified Method of Feasible Directions(MMFD) and Multi-Island Genetic Algorithm are employed as the algorithm for the airfoil optimization design.Three optimization design cases of transonic natural laminar flow airfoil are performed to validate the foregoing method. The first case uses an existing transonic laminar flow airfoil as the reference to optimize the initial NACA0012 airfoil. The second case optimizes the RAE2822 airfoil by the shape characteristic of the laminar airfoil. The third case optimizes the NACA0012 airfoil by the shape characteristic of the laminar airfoil. Results show that the optimization method can be more effective to optimize the laminar airfoil which can meet the on-design and off-design at the same time.This paper also has combined the natural laminar airfoil optimization method with 2.5 D design technology and carried out an optimization for the three-dimensional wing of a regional jet. The results indicate a remarkable aerodynamic improvement under the on-design condition.