CARo – Computational Aeroacoustics of Rotors
Institute of Aerodynamics and Gasdynamics, University of Stuttgart
Local Project ID:
HPC Platform used:
Hazeln Hen of HLRS
The helicopter and aeroacoustics group at IAG simulates the complex aerodynamics and aeromechanics of rotorcraft since the early 90s. Aeroacoustics have been added a couple of years later, with simulation technology nowadays utilising highly resolved CFD solutions, postprocessed for noise exposure at arbitrary observer points by means of the Ffowcs Williams-Hawkings approach.
Due to the extremely high demand of computational resources for acoustic simulations, those activities were forked off in 2017 from our long-running HELISIM project. Two years later, aerodynamics and aeroacoustics were re-united to simplify administrative burden, so this report constitutes the end of the separate CARo project.
During CARo, the noise emission of Contra-Rotating Open Rotors (CROR) have been investigated, especially in the installed case on an airliner tail, and predictive capability has been explored on the advanced compound configuration RACER from Airbus Helicopters, which is due for first flight in 2022.
Other results obtained within CARo were the detailed investigation of noise characteristics in different flight situations on more conventional helicopters, like the H145 in horizontal flight.
The spectra show the variation from mostly tonal noise with distinctive peaks during take-off (pls. see image below, left hand side) to broadband dominated sound in a horizontal flyover situation (right). Although some discrepancies exist, especially to higher frequencies, the agreement between flight test and simulation is sufficiently good to serve as an indicator of fundamental noise source mechanisms as well as their relative importance, depending on flight condition and emission direction. At the aircraft level, more silent rotors may be developed using this knowledge. From an operational point of view, the information obtained allows a flight path planning taking “quiet zones” into account, for example to avoid residential areas nearby.
The simulation technology developed and advanced in the helicopter group of IAG thus helps to further investigate the sound mechanisms of different rotorcraft and thus allows to diminish the noise impact on the community. Especially with regard to upcoming eVTOL concepts for Urban Air Mobility, so-called air taxis, which operate mostly close to inhabited areas, this capability is extremely important to assess different technologies under consideration at early design stages, before actual aircraft are built and further changes get extremely expensive in terms of money and delays.
Dr. Manuel Keßler, Dipl.-Phys.
Institut für Aerodynamik und Gasdynamik (IAG)
Pfaffenwaldring 21, D-70550 Stuttgart (Germany)
e-mail: kessler [@] iag.uni-stuttgart.de
Local project ID: GCS-CARo