Rotor blades and airfoils have to meet various requirements in the highly fluctuating wind field. At the same time there are requirements to be hold, like stability and robustness. Solutions of problems like these are not intuitve, so that optimization algorithms have be applied. Especially for airfoils smallest changes of the surface can determine important, flow relevant states, like the flow behaviour in stall and changes in lift and drag linked to this.
In combination with CFD the adjoint method is proposed. The advantage of this method in comparision with other optimization algorithms is the independence of the amount of equations, that have to be solved, from the amount of design parameters. Thus the grids used for the CFD calculations can be used as design
parameters directly, what poses a high amount of degrees of freedom for the optimization.