An inverse approach for airfoil Design

Inverse design methods directly compute geometry for specified design parameters such as surface pressure or velocity, which is related to the performance of an airfoil (or a blade) geometry. These methods replace the time consuming iterative procedure of direct methods in which a large number of different blade shapes are designed and analysed to find the one which creates the surface velocity or pressure distribution closest to the desired one. In this paper a viscous inverse method for airfoil design is described. The inverse design approach computes an airfoil shape based on the target surface pressure distribution. The re-design of an airfoil, starting from an initial arbitrary profile in subsonic flow regimes, demonstrates the merits and robustness of this approach. Keywords: inverse method, CFD, airfoil design, RANS equations. 1 Introduction The Computational Fluid Dynamics (CFD) codes can be directly used for airfoil shape design based on ‘trial and error’ approaches. By guessing an airfoil shape, the flow solution can be obtained using the CFD codes. The flow solution is then compared with the desired flow conditions. If these are not met then the airfoil geometry is altered. The whole process is repeated again, until the required flow conditions are achieved. In fact, these direct design procedures are very inefficient and time consuming. In order to reduce the development and design time and their associated costs, a more systematic method is required. The inverse method is an alternative approach that replaces the time consuming iterative procedure of direct methods. A pioneering airfoil inverse method based on conformal mapping was developed by Lighthill [1] in 1945. Since then many inverse methods for airfoil (or blade) design have been developed. These