Aerodynamic optimization design of airfoil using DFFD technique

This paper studies the directly manipulated free form deformation (DFFD) technique applied to airfoil geometry parameterization and aerodynamic shape optimization. By this method the direct manipulation and refined local shaping of an airfoil can be achieved, which overcomes the disadvantage of the traditional free form deformation (FFD) technique. The displacements of the FFD control points are computed by the least-square method using the specified displacements of some pilot points of the airfoil, so that the design variables are transformed from the FFD control points to the pilot points, which reduces the number of design variables when using a high order FFD control volume to achieve shape optimization. The case study shows that, compared with FFD, DFFD is of better physical intuition and geometry deforming capability. Finally, DFFD is applied to the aerodynamic shape optimization of RAE2822 airfoil together with a genetic algorithm, which shows that this approach is feasible and efficient, and it can be coupled with effective geometrical constraints.