Aeroelastic multidisciplinary design optimization of a swept wind turbine blade

Mitigating loads on awind turbine rotor can reduce the cost of energy. Sweeping blades produces a structural coupling between flapwise bending and torsion, which can be used for load alleviation purposes. Amultidisciplinary design optimization (MDO) problem is formulated including the blade sweep as a design variable. Amultifidelity approach is used to confront the crucial effects of structural coupling on the estimation of the loads. During theMDO, ultimate and damage equivalent loads are estimated using steady-state and frequency-domain-based models, respectively. The final designs are verified against time-domain full design load basis aeroelastic simulations to ensure that they comply with the constraints. A 10-MW wind turbine blade is optimized by minimizing a cost function that includesmass and blade root flapwise fatigue loading. The design space is subjected to constraints that represent all the necessary requirements for standard design of wind turbines. Simultaneous aerodynamic and structural optimization is performed with and without sweep as a design variable. When sweep is included in the MDO process, further minimizationof thecost function canbeobtained. Toshowthis achievement, a set of optimized straight blade designs is compared to a set of optimized swept blade designs. Relative to the respective optimized straight designs, the blademass of the swept blades is reduced of an extra 2% to 3% and the blade root flapwise fatigue damage equivalent load by a further 8%.