Open Access. Powered by Scholars. Published by Universities.®
Acoustics, Dynamics, and Controls Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 2 of 2
Full-Text Articles in Acoustics, Dynamics, and Controls
Reducing The Noise Impact Of Unmanned Aerial Vehicles By Flight Control System Augmentation, Matthew B. Galles
Reducing The Noise Impact Of Unmanned Aerial Vehicles By Flight Control System Augmentation, Matthew B. Galles
Mechanical & Aerospace Engineering Theses & Dissertations
The aim of this thesis is to explore methods to reduce the noise impact of unmanned aerial vehicles operating within acoustically sensitive environments by flight control system augmentation. Two methods are investigated and include: (i) reduction of sound generated by vehicle speed control while flying along a nominal path and (ii) reduction of acoustic exposure by vehicle path control while flying at a nominal speed. Both methods require incorporation of an acoustic model into the flight control system as an additional control objective and an acoustic metric to characterize primary noise sources dependent on vehicle state. An acoustic model was …
Computation Of Shock Induced Noise In Imperfectly Expanded Supersonic Jets, Bulent Imamoglu
Computation Of Shock Induced Noise In Imperfectly Expanded Supersonic Jets, Bulent Imamoglu
Mechanical & Aerospace Engineering Theses & Dissertations
Screech noise exists only in imperfectly expanded jets. The exit pressure of imperfectly expanded jets does not match ambient pressure, so expansion or compression waves appear out of the nozzle and generate shock cell patterns. Screech is generated by the interaction of shock cells and instability waves. Many experiments and computations have been done to model screech noise, but it is not yet a very well known subject.
A numerical study is performed to understand screech generation mechanisms and to compare with latest experiments. A supersonic underexpanded jet of 25.4 mm diameter is modeled for cases of Mach numbers of …