Multi-copters (drones) as a mean of public transportation, but also for package delivery, appears as a feasible and attractive way to better cope with an increased traffic load in densely populated areas. However, the acoustic emissions and aerodynamic behavior of these aircraft appear as two key aspects which require further research to respectively insure a broader acceptance by the population and a safe flying behavior in a city environment. As both the propulsion system and flying conditions to which these multi-copters are subjected differ from conventional aircraft, one cannot draw on earlier knowledge.
The DLR project AACID (acoustic and aerodynamics for city drones), therefore, aims at providing means to estimate the acoustic emissions and the aerodynamic performance of multi-copters operated in close proximity to urban areas. Of particular interest, is the investigation of the impact of cross-winds and wind gusts on the flying safety of the vehicles and their corresponding acoustic emissions.
The Institute of Aerodynamics and Flow Technology will conduct in cooperation with the Institute of Flight Guidance wind tunnel experiments as well as extensive numerical simulations to provide the necessary database to answer to the above research questions. The acoustic emissions of free-flying drones will be investigated in the semi-anechoic open test section of the Large Low-Speed Facility (DNW-LLF) wind tunnel in the Netherlands. Complementary aerodynamic performance and acoustic emission measurements on a generic multi-propeller setup will take place in the Aeroacoustic Wind Tunnel Braunschweig (AWB) of the Institute of Aerodynamics and Flow Technology. Aerodynamic and acoustic interference effects in multi-propeller configurations will be investigated using numerical simulations by the Institute. The resulting database will serve as reference for the development of a semi-empirical acoustic prediction model for multi-propeller drones as well as a scaling methodology for the evaluation of full-scale multi-copter transportation systems in urban situations.