Towards Efficient Aerodynamic and Aeroacoustic Optimization for Urban Air Mobility Vehicle Design
B. Pacini, A. Yildirim, B. Davoudi, J. R. R. A. Martins, and K. Duraisamy
AIAA Aviation Forum 2021, 2021
Urban air mobility vehicles have taken form as advanced rotorcraft with sets of wings, rotors, canards, and other appendages. Noise generation is an important technical barrier that must be addressed to prevent these vehicles from causing excessive disturbance to the communities they are intended to service. There is a need for efficient and low-fidelity analysis tools specifically for the conceptual design and sizing phase of urban air mobility vehicle development. Such tools must be computationally efficient to allow for repeated analyses needed for design optimization. This paper presents coupled aerodynamic and aeroacoustic analysis formulated for gradient-based design optimization. Rotor performance is modeled using HELIX, a hybrid blade element momentum theory tool, coupled with PULSE, an aeroacoustic analysis tool based on the Ffowcs Williams and Hawkings aeroacoustic analogy, reformulated as Farassat Formulation 1A. This work presents a methodology for computing implicit derivatives of the coupled aerodynamic and aeroacoustic models implemented within the software package OpenMDAO. Both models are validated independently, and derivatives are verified using finite difference and complex step approximations. These tools are used to analyze and optimize the rotors on the single passenger NASA N+1 quadrotor vehicle with respect to blade-shape parameters. This paper aims to introduce aeroacoustic analysis into gradient-based optimization efficiently and demonstrate the impact that such optimization can have for minimizing the noise footprint of an urban air mobility vehicle.