Aerodynamic shape optimization of wind turbine rotor blades using the continuous adjoint method

This paper presents the development of the continuous adjoint method for incompressible fluid flows, solved for the absolute velocity in the relative reference frame, allowing the optimization of rotating machines. The development is conducted using an extended version of the OpenFOAM-based continuous adjoint solver adjointOptimisationFoam. This implements and solves the adjoint to the Navier-Stokes system of equations, coupled with the differentiation of the Spalart-Allmaras turbulence model. Its application to the aerodynamic shape optimization of the MEXICO and NREL Phase VI wind turbines blades follows, targeting the maximization of the axial moment. The flow solution for the two cases is compared with the outcome of other CFD solvers and experimental data, where available. Blades and the displacements of the surrounding grid nodes are parameterized using a volumetric B-Splines morphing box. A number of optimizations are conducted using different operating conditions and geometric constraints.