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Analysis of simultaneous measurement of acousticpressure in the far-field and density gradient in thenear-field in a cold jet
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2012 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The purpose of the investigation presented here is to study the degree of correlation between the density gradient in the near eld and the aeroacoustic sound generation in the far eld of a cold jet. The variations of the density gradient in the ow are visualized and  recorded by the Background Oriented Schlieren (BOS) technique. In this method high power LEDs are used as illumination source. Simultaneously the pressure uctuations in the acoustic far-eld are recorded by a set of microphones. Measurements on a round nozzle and a chevron nozzle are conducted and the obtained results are compared. Large structures emitting noise are localized, being in the case of the chevron nozzle further upstream due to the higher level of entrainment of the jet with the surrounded ambient uid. In addition, it is demonstrated that the noise produced by these structures is radiated mainly downstream, having the highest correlations with the pressure uctuations recorded with the microphone located at an angle Ø= 26X respect to the jet-axis.

Place, publisher, year, edition, pages
2012. , 15 p.
Trita-AVE, ISSN 1651-7660 ; 2012:72
National Category
Aerospace Engineering
URN: urn:nbn:se:kth:diva-118799OAI: diva2:608463
Educational program
Master of Science - Aerospace Engineering
Available from: 2013-02-27 Created: 2013-02-27 Last updated: 2013-02-27Bibliographically approved

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