NASA’s Advanced Air Transport Technology Project has worked with industry over the last decade to develop airframe/propulsion concepts and associated technologies to enable transformative air travel for future generations. Techsburg and AVEC’s proposal “Design Cycle Prediction Software for Wing-Strut Junction Flow Noise” addresses a technology analysis gap in the development of a leading airframe concept, the Transonic Truss Braced Wing (TTBW) airliner. The aeroacoustic signatures of the large bracing strut and jury member features of this configuration need to be captured in reduced-order modeling tools to enable design cycle trade studies/optimization of far field noise due to the wing/strut junction noise source. Building on Phase I success, we propose to train an artificial neural network (ANN) model of this noise source using PowerFLOW lattice-Boltzmann method (LBM) computational aeroacoustic simulations. Phase II will conclude with delivery of the reduced-order software tool Wing-Strut Broadband Acoustic Model, “WiSBAM”.
To document noise characteristics and provide validation data for acoustic modeling of rotor systems appropriate for eVTOL/UAM aircraft, the team of Techsburg, AVEC, and Virginia Tech performed an outdoor static test of a subscale 5-blade rotor. The testing was carried out as part of a program to demonstrate feasibility and performance of a quiet rotor system in support of the eVTOL industry. Techsburg designed a low-tip speed rotor to approximate performance required by a 4-5 passenger UAM vehicle. A driving design feature was low-tip speed operation (Mtip ~0.27) at system disk loadings of 7 to 8 psf (~3.7 N/m2). The test article was designed as a ground adjustable pitch 5-blade rotor, and 2-blade and 3-blade versions of this rotor were also tested during this project. The test article size of 3 feet diameter (0.91 m) represented a scale factor of approximately 30% compared to a full size vehicles currently in operation or development today. The aerodynamic performance in hover was consistent with other rotor systems tested in the past at Techsburg (Figure of Merit ~0.70), and the effects of naturally occurring turbulence on rotor acoustics was measured using a 180-deg arc array of ground plane microphones at the Virginia Tech Drone Park test facility. The paper closes with a discussion of simulating the experiment with the PowerFLOW LBM solver with and without flow turbulence.