The team of Techsburg, AVEC, and Virginia Tech propose a program that directly complements the recent NASA/Joby Aviation flight test program by studying isolated low tip speed tiltrotor noise in detail, with an initial primary objective of the development and validation of scaling methods to extend tests and models to full-scale applications, including noise sources due to ingestion of naturally occurring turbulence at hover conditions. The Phase I/Phase II program will make use of test methods in an outdoor environment in addition to numerical methods based on the PowerFLOW LBM flow solver as developed by the Techsburg, AVEC, and Virginia Tech team. Our goal is the development of a family of low-noise propulsors for eVTOL applications. These airframe-agnostic propulsors would have documented aerodynamic and acoustic characteristics, measured in real atmospheric conditions with atmospheric turbulence, thereby removing approximations in for future vehicle performance and noise signature in early design phases. By supplying these as “off-the-shelf” products to the eVTOL industry, much of the expensive R&D related to quiet propulsors could be eliminated and commodified for the industry.
With our experience in full-aircraft modeling, we believe there is a compelling case for individual component testing. Full aircraft modeled in simple hover cases with no relative wind or turbulence result in a very complex flow fields. Despite this complexity, some of these interaction phenomena may not be the dominant noise source producers, and it is difficult to gain insight and understand primary noise generation mechanisms this way. By focusing on the single most important noise source for these vehicles, detailed study of the acoustic characteristics of isolated rotors with naturally occurring turbulence ingestion will greatly advance overall understanding of eVTOL noise production by helping to avoid overly complex aerodynamic interactions, even for simple hover cases.
The tiltrotor geometry developed by Techsburg offers a non-proprietary test geometry to NASA. In addition, as early as Phase I, data produced in the tiltrotor development program will provide detailed validation datasets over a range of sizes for NASA. This data can be used for tool developers and the eVTOL/UAM community at large. The test program will offer complementary data to the Joby S4 dataset (Pascioni et. al. 2022) for investigation of single rotor vs. full-aircraft configuration acoustics.
The development of a commercially available low-noise, high-efficiency tiltrotor system with documented performance would have great value and impact future eVTOL development companies by lowering their cost to entry in the market. Scaling approaches developed would provide the aeroacoustic community methods for scaling noise with propulsor or fan sizes, such as for the HVAC industry.