Numerical analyses of suppression of sound emission by interference between a pair of helicalmodes in a supersonic jet

2014 Fiscal Year Final Research Report

• Project/Area Number: 24560189
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Fluid engineering
• Research Institution: University of Toyama
• Principal Investigator: WATANABE Daisuke 富山大学, 大学院理工学研究部(工学), 講師 (70363033)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 超音速ジェット / マッハ波 / 空力騒音 / 線形安定性解析 / DNS / CFD

Outline of Final Research Achievements

The numerical results provide new physical features of the Mach wave generated in supersonic round jets, which lead to extinction of the Mach wave by introducing disturbance condition. Upstream disturbance conditions play an important role for the emission of the Mach wave in supersonic jets. The pressure fluctuations generated by the growth of the opposite helical mode are shown to be linearly superimposed into the jet near sound field. The numerical results indicate that the jet forced with a pair of first helical modes can indicate the elimination of Mach waves at restricted emission azimuthal angles due to the interference of these modes. The partial elimination of the Mach wave also appears in a turbulent jet at the frequency of the artificially forced an optimal combination of the helical modes at the inlet region. This forcing technique will be extended to the Mach wave reduction in the distinct azimuthal direction.

Free Research Field

工学