On the Distribution and Scaling of Convective Wavespeeds in the Shear Layers of Heated Supersonic Jets

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• 作者：Tobias Ecker ; K. Todd Lowe ; Wing F. Ng
• 关键词：Jet noise ; Supersonic shear layers ; Radiation efficiency
• 刊名：Flow, Turbulence and Combustion
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：98
• 期：2
• 页码：355-366
• 全文大小：
• 刊物类别：Engineering
• 刊物主题：Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer; Automotive Engineering;
• 出版者：Springer Netherlands
• ISSN：1573-1987
• 卷排序：98

文摘

The noise generated by supersonic plumes is of growing concern given the enormous peak noise intensity radiated by tactical aircraft engines. A key component of this noise is the enhanced radiation of mixing noise caused by large scale eddies convecting supersonically relative to the surrounding quiescent medium. As very little data exist for eddy convection in high Reynolds number, supersonic plumes, our current ability to develop concepts that alter compressible eddy convection is limited. Herein we present new experimental data of eddy convective wavespeeds in the developing shear layer of supersonic heated jets. A new scaling of the wavespeed in radial similarity coordinates is proposed which takes into account the influence of the ratio of static densities between the jet and ambient streams. In particular, we observe a structural change in wavespeed spectra at the end of the potential core—in addition to high turbulence levels, the potential core breakdown region can have enhanced eddy wavespeeds, increasing noise radiation efficiency. The results provide a first examination of the interplay of density ratio effects and the dynamic breakdown process of the potential core in supersonic jets—physics integral to the noise generation process.