Open Access. Powered by Scholars. Published by Universities.®
- Discipline
Articles 1 - 4 of 4
Full-Text Articles in Physics
Time-Domain Characterization Of Nonlinear Propagation In Military Aircraft Jet Noise, Brent Owen Reichman
Time-Domain Characterization Of Nonlinear Propagation In Military Aircraft Jet Noise, Brent Owen Reichman
Theses and Dissertations
Nonlinear propagation and shock formation are shown in noise radiated from full-scale military jet aircraft. Perception of sound is not only affected by the overall sound pressure level of the noise, but also characteristics of the sound itself. In the case of jet noise, acoustic shocks within the waveforms result in a characteristic commonly referred to as"crackle." The origin of shocks in the far-field of jet noise is shown to be through nonlinear propagation. Metrics characterizing the shock content of a waveform are explained and given physical significance, then applied to jet noise at various distances and engine conditions to …
Vector Intensity And Holography-Based Acoustic Source Characterization Of A Military Jet Aircraft, Trevor Alden Stout
Vector Intensity And Holography-Based Acoustic Source Characterization Of A Military Jet Aircraft, Trevor Alden Stout
Theses and Dissertations
The scientific community has employed multiple methods to analyze and describe the jet noise emanating from the turbulent exhaust flow from modern military aircraft engines, with the goal that better characterization of the sound radiation will improve noise reduction efforts. This thesis utilizes three different approaches to characterize the noise source region from a static F-22A Raptor. First, the energy flow field along planes near the aircraft and along an arc is measured using a multidimensional vector intensity probe. The resulting vector intensity maps give a clear indication of the directionality of the noise as a function of frequency at …
Array-Based Characterization Of Military Jet Aircraft Noise, David William Krueger
Array-Based Characterization Of Military Jet Aircraft Noise, David William Krueger
Theses and Dissertations
Since the 1950s the jet aeroacoustics community has been involved in predicting and measuring the noise distribution in jets. In this work, cylindrical and planar Fourier near-field acoustical holography are used to investigate radiation from a full-scale, installed jet engine. Practical problems involving measurement aperture and the highly directional nature of the source are addressed. Insights from numerical simulations reveal usable reconstruction regions. A comparison of cylindrical and planar NAH for the respective measurement apertures shows cylindrical NAH outperforms planar NAH on reconstructions both towards and away from the source.
The Effect Of Nonlinear Propagation On Near-Field Acoustical Holography, Micah Raymond Shepherd
The Effect Of Nonlinear Propagation On Near-Field Acoustical Holography, Micah Raymond Shepherd
Theses and Dissertations
Near-field acoustical holography (NAH) has been used extensively for acoustical imaging of infinitesimal-amplitude (or small-amplitude) sources. However, recent interests are in the application of NAH to image finite-amplitude (or high-amplitude) sources such as jets and rockets. Since NAH is based on linear equations and finite-amplitude sources imply nonlinear effects, which cause shock formation and consequently an altered spectral shape, a feasibility study is carried out to determine the effect of nonlinear propagation on NAH. Jet and rocket sources typically have a distinct spectral shape resembling a ‘haystack’ and center frequencies varying from 30 to 300 Hz. To test the effect …