Turbulent jet interaction with a long rise-time pressure signature

Ukai, T., Ohtani, K. and Obayashi, S. (2016) Turbulent jet interaction with a long rise-time pressure signature. Applied Acoustics, 114, pp. 179-190. (doi: 10.1016/j.apacoust.2016.07.015)

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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.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Ukai, Dr Takahiro
Authors: Ukai, T., Ohtani, K., and Obayashi, S.
College/School:College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
Journal Name:Applied Acoustics
Published Online:03 August 2016
Copyright Holders:Copyright © 2016 Elsevier
First Published:First published in Applied Acoustics 114:179-190
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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