Techsburg presents paper at the Vertical Flight Society's 78th Annual Forum entitled “Measured Acoustic Characteristics of Low Tip Speed eVTOL Rotors in Hover”


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.