Abstract
Multidisciplinary design optimization (MDO) was performed on a helicopter rotor blade. The blade was modeled as a rigid flapping blade for dynamics; Blade Element Theory (BET) was the analysis approach to model the aerodynamic loading, and a simple linearly elastic hollowed rectangular section was the main structural component. MATLAB was used to solve the flapping differential equations and its Sequential Quadratic Programming (SQP) and Genetic Algorithm (GA) were used for the optimization. A Particle Swarm Optimization (PSO) routine was also tested. The optimization process consisted of three cases. The first case was a simple cantilever beam under centrifugal and an assumed bending loads. The optimization was performed using the SQP, GA, and PSO algorithms. The SQP resulted in the superior design with 75.45 compared to the GA's 87.1 and the PSO's 79.2, but a local minimum was present. The second case was an expansion of the first case by turning it into multidisciplinary problem. Aerodynamics was included in the design variables and objective function. Only the SQP algorithm was used and there was a reduction in hub vertical shear by 33.6%. The blade mass increased by 36.84%. The last case was an improvement to the second by creating a multiobjective problem by including the hub radial shear and the results were improved significantly by reducing the hub vertical shear by 34.06% and radial shear by 17.87% with a reduction of blade mass by 23.86%.
Highlights
The helicopter plays a crucial role in a wide variety of activities such as military, recreation, and medical transport
The objective of this case will be to minimize the structural mass under an assumed aerodynamic loading and to compare the Sequential Quadratic Programming (SQP), Genetic Algorithm (GA), and Particle Swarm (PS) algorithms
Everything from aerodynamics, dynamics and aeroelasticity are included with varying degrees of fidelity. It is an excellent book and is highly recommended to anyone who wishes to learn more about rotorcraft
Summary
The helicopter plays a crucial role in a wide variety of activities such as military, recreation, and medical transport. The blade structure and aerodynamics are unsteady, even in steady level flight conditions there is an imbalance of aerodynamic loads with air flow velocities ranging from transonic to low speed including stall and reversed flow. Because of these coupled interactions, the helicopter rotor design process is highly multidisciplinary in nature and requires the merging of several disciplines. The second case will be a MDO problem by incorporating the aerodynamics and dynamic disciplines. The objective of this case is to reduce the hub vertical shear. In addition interaction between rotor and the fuselage further complicates helicopter system predictions (13)
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