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RISS 인기검색어
- 검색키워드
- 저자 : Iman Bahman Jahromi (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
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Reflected shock tube experiments on aeroacoustic signature of hot jets
Iman Bahman Jahromi,Mohammad Ebrahimi,Kaveh Ghorbanian 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8
We used a reflected shock tube to investigate the acoustic signature of a hot jet at the far-field. Experiments were performed at Mach = 1.4 and a total temperature of T t = 950 Kelvin. Far-field acoustic signatures of the hot jet at six polar angles θ = 15˚ to θ = 90˚ from the jet axis) were measured and imaged by the means of continuous wavelet transform in scalograms. The results were compared with experiments from a steady test facility at similar test conditions. Further, the primary characteristics of noise events in jet far-field were compared with analytical models considering wavepacket as the main source of jet noise. The results indicate that higher frequency events at θ = 90˚ occur with a small time shift relative to the low azimuthal mode base event. This phenomenon might be the main reason why the acoustic signal at the side angles behaves more noisily than at low polar angles.
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A new insight into design of acoustic liner arrays arrangement in the presence of a grazing flow
Hadi Dastourani,Iman Bahman-Jahromi Techno-Press 2023 Advances in computational design Vol.8 No.4
This study evaluated the acoustic performance of two configurations of serial HR arrays and lined HR arrays in the presence of grazing flow using a 3D numerical simulation. The dual, triple, and quad HR arrays were compared to the conventional HR array. The simulation results showed that the number of resonant frequencies increased with the number of serial HR arrays. The C<sub>TL</sub> did not significantly change with the number of serial HR arrays. The acoustic performance of the two, three, and four-lined HR arrays was compared to the conventional HR array. The results showed that the resonant frequency and TLmax increased with the number of lined HR arrays. The C<sub>TL</sub> also increased with the number of lined HR arrays. The effect of the grazing flow Mach number (M<sub>a</sub>) was investigated on the four-lined HR array configuration and compared to the conventional HR configuration. TLmax and C<sub>TL</sub> decreased for both configurations with increasing M<sub>a</sub>. The four-lined HR array configuration had significantly better acoustic performance than the conventional HR configuration. The TLmax and C<sub>TL</sub> increased by more than 300% when the configuration was changed from the conventional HR to the four-lined HR array at M<sub>a</sub> = 0.The increment percentage decreased with increasing M<sub>a</sub>.
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