CFD Based Wing Shape Optimization Through Gradient-Based Method

1. Abstract This paper deals with the optimization of shape of aerodynamic profiles. The objective is to reduce the drag coefficient on a given airfoil while preserving the lift coefficient within acceptable ranges. A set of control points defining the geometry are passed and parameterized as a B-Spline curve. These points are modified automatically by means of CFD analysis. A given shape is defined by an user and a valid volumetric CFD domain is constructed from this planar data and a set of user-defined parameters. The construction process involves the usage of 2D and 3D meshing algorithms that were coupled into owncode. The volume of air surrounding the airfoil and mesh quality are also parametrically defined. Some standard NACA profiles were used by obtaining first its control points in order to test the algorithm. Navier-Stokes equations were solved for turbulent, steady-state flow of compressible fluids using the k-epsilon model and SIMPLE algorithm. In order to obtain data for the optimization process an utility to extract drag and lift data from the CFD simulation was added. After a simulation is run drag and lift data are passed to the optimization process. A gradient-based method using the steepest descent was implemented in order to define the magnitude and direction of the displacement of each control point. The control points and other parameters defined as the design variables are iteratively modified in order to achieve an optimum. Preliminary results on conceptual examples show a decrease in drag and a change in geometry that obeys to aerodynamic behavior principles. 2.