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Oscillations in the near field of a heated two-dimensional jet

Published online by Cambridge University Press:  26 April 2006

Ming-Huei Yu  and
Peter A. Monkewitz
Ming-Huei Yu
Affiliation:
Department of Mechanical, Aerospace and Nuclear Engineering, University of California, Los Angeles, CA 90024-1597, USA Current address: Mechanical Engineering Department, National Sun Yat-Sen University, Kaohsiung, Taiwan 80424.
Peter A. Monkewitz
Affiliation:
Department of Mechanical, Aerospace and Nuclear Engineering, University of California, Los Angeles, CA 90024-1597, USA Current address: Department of Mechanics, ME-Ecublens, Federal Institute of Technology, CH-1015 Lausanne, Switzerland.
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Abstract

A two-dimensional hot-air jet is investigated experimentally in the transitional regime. The density effect on the near-field behaviour of the initially laminar jet is explored by flow visualization, mean flow measurements and spectral analysis of fluctuating data. It is shown that the broadband amplitude spectra which characterize cold jets become line-dominated for hot jets when the ratio of the jet-exit to the ambient density is below approximately 0.9. Below this critical density ratio the oscillations in the hot jet are shown to be self-excited. That is, the onset of the global oscillations is identified as a Hopf bifurcation and the critical parameter is determined from amplitude spectra and autobicoherence, with the latter proving to be more reliable. Furthermore, the development of three-dimensional structures, which contribute to the jet spreading, is revealed by flow visualization. It is found that, for the parameters investigated, the spreading of the two-dimensional hot jet is not as spectacular as in the axisymmetry case.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 255 , October 1993 , pp. 323 - 347
Copyright
© 1993 Cambridge University Press

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