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Plane turbulent buoyant jets. Part 2. Turbulence structure

Kotsovinos, Nikolas E. (1977) Plane turbulent buoyant jets. Part 2. Turbulence structure. Journal of Fluid Mechanics, 81 (1). pp. 45-62. ISSN 0022-1120. doi:10.1017/S0022112077001906.

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The turbulence structure of a plane vertical buoyant jet in the transition state from jet-like to plume-like growth is the object of this investigation. The ambient fluid is of uniform density and motionless except for the flow induced by the jet. An analysis of the turbulence energy equation reveals that the production of turbulent energy by the buoyancy forces relative to the production by the shear stress increases as the jet Richardson number increases, and becomes constant for a plume-like buoyant jet. A systematic set of experiments was carried out to examine the turbulence structure for a wide range of initial Richardson numbers, extending from a value appropriate to a jet-like flow (very close to zero) to that appropriate for a plume-like flow (approximately 0·6). Fast-response thermistors and a laser-Doppler velocimeter were used to measure the buoyant jet's temperature and velocity respectively. The temperature and velocity data were recorded magnetically in digital form and subsequently processed to extract both mean and fluctuating values. The turbulence intensity and the probability density distribution of the temperature and velocity fluctuations, the maximum and minimum temperature, the intermittency, and the frequency of crossing of the hot/cold and the cold/hot interface of a buoyant jet were investigated. It was determined that the intensity of temperature and velocity fluctuations increases with increasing Richardson number. An explanation is suggested for the large-scale vortices observed in a plume.

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Additional Information:Copyright © 1977 Cambridge University Press. Reprinted with permission. (Received 28 January 1976 and in revised form 9 June 1976) The subject of this paper is taken in part from the author’s Ph.D. thesis, submitted to the California Institute of Technology. The author is grateful to Professor E.J. List for many constructive and enlightening discussions. The financial support of the National Science Foundation (Grant ENG75-02985) is also gratefully acknowledged.
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Deposited On:04 Oct 2006
Last Modified:08 Nov 2021 20:23

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