Turbulent jet interaction with a long rise-time pressure signature

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• 作者：Takahiro Ukai^a ; ^b ; ^{Takahiro.Ukai@glasgow.ac.uk" class="auth_mail" title="E-mail the corresponding author} ; Kiyonobu Ohtani^a ; Shigeru Obayashi^a
• 关键词：Shock-turbulence interaction ; Low sonic boom signature ; Ballistic range facility
• 刊名：Applied Acoustics
• 出版年：2016
• 出版时间：15 December 2016
• 年：2016
• 卷：114
• 期：Complete
• 页码：179-190
• 全文大小：3449 K

文摘

A sonic boom signature with a long rise time has the ability to reduce the sonic boom, but it does not necessarily minimize the sonic boom at the ground level because of the real atmospheric turbulence. In this study, an effect of the turbulence on a long rise-time pressure signature was experimentally investigated in a ballistic range facility. To compare the effects of the turbulence on the long and short rise-time pressure signatures, a cone-cylinder projectile that simultaneously produces these pressure signatures was designed. The pressure waves interacted with a turbulent field generated by a circular nozzle. The turbulence effects were evaluated using flow diagnostic techniques: high-speed schlieren photography, a point-diffraction interferometer, and a pressure measurement. In spite of the fact that the long and short rise-time pressure signatures simultaneously travel through the turbulent field, the turbulence effects do not give the same contribution to these overpressures. Regarding the long rise-time pressure signature, the overpressure fluctuation due to the turbulence interaction is almost uniform, and a standard deviation 1.5 times greater than that of the no-turbulence case is observed. By contrast, a short rise-time pressure signature which passed through the same turbulent field is strongly affected by the turbulence. A standard deviation increases by a factor of 14 because of the turbulence interaction. Additionally, there is a non-correlation between the overpressure fluctuations of the long and short rise-time pressure signatures. These results deduce that the length of the rise time is important to the turbulence effects such as the shock focusing/diffracting.