High-Fidelity Multidisciplinary Design Optimization of Low-Noise Rotorcraft

A high-fidelity multidisciplinary analysis and optimization methodology is presented for low-noise rotorcraft design. Tightly coupled discipline models include physics-based computational fluid dynamics, rotorcraft comprehensive analysis, and acoustic-noise prediction and propagation. A discretely-consistent adjoint methodology accounts for sensitivities of the unsteady flow and unstructured, dynamically deforming, overset grids. The sensitivities of structural responses to blade aerodynamic loads are computed using a complex-variable approach. Sensitivities of the acoustic metrics are computed by manual differentiation. Interfaces are developed to enable interactions between the coupled discipline models for rotorcraft aeroelastic and aeroacoustic analysis and the integrated sensitivity analysis. The multidisciplinary sensitivity analysis is verified through a complex-variable perturbation approach. A gradient-based optimization for a HART-II rotorcraft configuration in a forward-flight condition is demonstrated with the objective of reducing a rotorcraft noise metric of interest, subject to aerodynamic and geometric constraints. The optimized configuration achieves a notable noise reduction and satisfies all required constraints. Computational cost of the optimization cycle is assessed in a high-performance computing environment and found to be acceptable for design of rotorcraft in general level-flight conditions.