Optimization of rotor blades for combined structural,dynamic, and aerodynamic properties

A helicopter is intrinsically interdisciplinary due to the close coupling among aerodynamics, dynamics, and the blade structural details. Therefore a design optimization with proper interactions among appropriate disciplines (such as structure, dynamics, and aerodynamics) can offer significant benefit to improve rotor performance. This paper studies the integration of structure, dynamics, and aerodynamics in design optimization of helicopter rotor blades. The optimization is performed to minimize the rotor power required and to satisfy design requirements from structure (minimum blade weight and safe stress margin and fatigue life) and dynamics (proper placement of blade natural frequencies and free of flutter). An effort is made to formulate an effective strategy for combining these various requirements in the optimization process. The paper also presents a way for an intelligent phasing of this interdisciplinary optimization to overcome the hurdles due to conflicting demands on the design variables which arise from different disciplines.Notation nondimensional leading edge mass size, = a/R - C _T rotor thrust coefficient - C _P rotor power coefficient - nondimensional chord, =c/R - nondimensional lumped mass size, =d/R - F(x) objective function - G _j (x) j-th inequality constraint function - H _j (x) j-th equality constraint function - R blade radius, meters - nondimensional blade radial coordinate, =r/R - nondimensional web thickness, =s ₁/R - nondimensional web thickness, =s ₂/R - t nondimensional flange thickness, =t/R - x vector of design variables - x _i i-th component of vector of design variables - blade pitch angle