Time-dependent Aero-acoustic Adjoint-based Shape Optimization of Helicopter Rotors in Forward Flight

A formulation for the sensitivity analysis of time-dependent helicopter rotor aeroacoustic problems is presented in this paper. The hybrid aeroacoustic approach, in which a near body CFD solver is coupled to an FW-H acoustic module that propagates the rotor noise signature to a far field observer, has been followed in this work. Both forward and adjoint sensitivity formulations are derived that correspond to analogues of the aeroacoustic analysis problem. The fully coupled aeroacoustic analysis formulation is first verified to effectively perform noise predictions of a four bladed HART2 rotor in trimmed forward flight. Upon successful verification, the adjoint formulation is used to minimize helicopter rotor noise signatures via blade shape optimization.

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