INTEGRATED AERODYNAMIC LOAD DYNAMIC OPTIMIZATION OF HELICOPTER ROTOR BLADES

An integrated aerodynamic load/dynamic optimization procedure is used to minimize blade weight and 4 per rev vertical hub shear for a rotor blade in forward flight. Through the coupling of aerodynamic loads and dynamics into the optimization procedure, the effects of changes in air loads due to changes in the design variables are incorporated. Both single and multiple objective functions are used in the optimization formulation. The "Global Criteria Approach" is used to formulate the multiple objective optimization, and results are compared with those obtained by using single objective function formulations. Constraints are imposed on natural frequencies, autorotational inertia, and centrifugal stress. The program CAMRAD (Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics) is used for the blade aerodynamic and dynamic analyses, and the program CONMIN is used for optimization. The vertical air load distributions on the blade, before and after optimization, are compared. The total power required by the rotor to produce the same amount of thrust per area is also calculated before and after optimization. Results of this study indicate that integrated optimization can significantly reduce the blade weight and vertical hub shear as well as oscillatory vertical blade air load distributions and the total power required.