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An experiment was carried out to analyse and compare the screech tone characteristics and schlieren structures of an under-expanded jet flowing through four rectangular nozzles, aspect ratios of which are different (having the same height but different widths), with the jet pressure ranging from 0.2 to 0.8 MPa. Results indicate that there exist two different screech tone modes in the noise generated by supersonic jet flowing through the rectangular nozzles with different aspect ratios, and a mode switching can be found by altering the jet pressure. Mode switching is a phenomenon that different mode dominates or disappears according to the change of jet pressure. The switching time of fundamental frequencies in the screech tone modes and the width of the domination interval would be shortened as the aspect ratio decreases. The jet flow pressure drop interval of one mode, whose aspect ratio is 2, is extremely small. This phenomenon has never been mentioned in the literature. When the aspect ratio of the rectangular nozzle is 4, there exists an interruption and skip on the fundamental frequency-jet pressure curve within the jet flow domination interval for jet pressure at 0.49 MPa. As the pressure reduces, the axes of the schlieren figures begin to shake, and the structure stability of the flow field with different aspect ratio varies with the jet pressure. When the jet pressure is within the range of 0.45 to 0.70 MPa, the density in the first shock-cell decreases as the aspect ratio reduces. Meanwhile, axial pulsation and disorder of the flow field behind the second shock-cell appear. When the jet pressure is under 0.45 MPa, the flow field structure of the shock wave becomes more stable as the aspect ratio increases. In this pressure region, the periodical shock-cell structure is weaker than those above 0.45 MPa. Analyzing the screech frequency spectrum and the schlieren figures, we can find that the second and third shock-cells also have feedback and enhancement for the sound pressure of the screech frequency.
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Keywords:
- supersonic jet /
- screech switch /
- shock wave /
- disturbance wave
[1] Tam C K W 1998 Theoret.Comput.Fluid Dynam. 10 393
[2] Powell A 1953 Proceedings Phys .Soc .London. 66 1039
[3] Powell A 1953 Journal Acoust .Soc.An. 25 385
[4] Tam C K W 1995 Annu.Rev.Fluid Mech. 27 17
[5] He F, Hao P F, Zhang X W 2003 Acta Acustica 28 182 (in Chinese) [何枫, 郝鹏飞, 张锡文 2003 声学学报 28 182]
[6] Zhang Q, Chen X, He L M, Rong K 2013 Acta Phys. Sin. 62 084706 (in Chinese) [张强, 陈鑫, 何立明, 荣康 2013 物理学报 62 084706]
[7] Berland J, Bogey C, Bailly C 2006 12th AIAA/CEAS Aeroacoustics Conference Cambridge, UN, May 8-10 2006 p2496
[8] Panda J, Raman G, Zaman K B M Q 2004 NASA/TM 2004-212481
[9] He F, Xie J S, Yao C H 2002 J. Propulsion Technol. 29 98 (in Chinese) [何枫, 谢俊石, 姚朝晖 2002 推进技术 29 98]
[10] Cui X G, Yao C H 2008 J. Propulsion Technol. 29 98 (in Chinese) [崔新光, 姚朝晖 2008 推进技术 29 98]
[11] Zhang B Ji H H 2005Journal of Aerospace Power 20 0104 (in Chinese) [张勃, 吉洪湖 2005 航空动力学报 20 0104]
[12] Zhang B, Ji H H, Cao G Z, Huang W 2010 Journal of Aerospace Power 25 2244 (in Chinese) [张勃, 吉洪湖, 曹广州, 黄伟 2010 航空动力学报 25 2244]
[13] Zhu Y Z, Yi S H, He L, T L F, Zhou Y W 2013 Chin. Phys. B 22 014702
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[1] Tam C K W 1998 Theoret.Comput.Fluid Dynam. 10 393
[2] Powell A 1953 Proceedings Phys .Soc .London. 66 1039
[3] Powell A 1953 Journal Acoust .Soc.An. 25 385
[4] Tam C K W 1995 Annu.Rev.Fluid Mech. 27 17
[5] He F, Hao P F, Zhang X W 2003 Acta Acustica 28 182 (in Chinese) [何枫, 郝鹏飞, 张锡文 2003 声学学报 28 182]
[6] Zhang Q, Chen X, He L M, Rong K 2013 Acta Phys. Sin. 62 084706 (in Chinese) [张强, 陈鑫, 何立明, 荣康 2013 物理学报 62 084706]
[7] Berland J, Bogey C, Bailly C 2006 12th AIAA/CEAS Aeroacoustics Conference Cambridge, UN, May 8-10 2006 p2496
[8] Panda J, Raman G, Zaman K B M Q 2004 NASA/TM 2004-212481
[9] He F, Xie J S, Yao C H 2002 J. Propulsion Technol. 29 98 (in Chinese) [何枫, 谢俊石, 姚朝晖 2002 推进技术 29 98]
[10] Cui X G, Yao C H 2008 J. Propulsion Technol. 29 98 (in Chinese) [崔新光, 姚朝晖 2008 推进技术 29 98]
[11] Zhang B Ji H H 2005Journal of Aerospace Power 20 0104 (in Chinese) [张勃, 吉洪湖 2005 航空动力学报 20 0104]
[12] Zhang B, Ji H H, Cao G Z, Huang W 2010 Journal of Aerospace Power 25 2244 (in Chinese) [张勃, 吉洪湖, 曹广州, 黄伟 2010 航空动力学报 25 2244]
[13] Zhu Y Z, Yi S H, He L, T L F, Zhou Y W 2013 Chin. Phys. B 22 014702
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