Aerodynamic Shape Optimization of Hovering Rotors Using a Discrete Adjoint of the RANS Equations

In this paper, a gradient-based method using an adjoint formulation of the RANS equations is applied to the problem of helicopter blade shape optimization in hover. Flow analysis is briefly reminded and the adjoint vector method used throughout this study is presented. Then, the optimization procedure coupling a gradient-based optimizer and the adjoint solver is described. The method is applied to the planform optimization of two different rotor blades. Geometrical laws like twist, chord, anhedral and sweep distributions over the blade span are used. The method appears to be efficient in terms of CPU-time and memory savings and reveals to be able to provide interesting optimum shape for rotor blade. The main interest of the present method is its ability to perform local optimization of isolated rotor in hover flight using an accurate CFD model and accounting for a large number of shape parameters