Atthanayake, Iresha (2018) Behaviour of an axi-symmetric jet in the rotating reference frame. PhD thesis, University of Warwick.

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Abstract

Experimental results from comprehensive PIV measurements investigating the dynamics of turbulent jets in a rotating fluid are presented. It is observed that background system rotation induces a time-periodic formation-breakdown cycle of the jets. The flow dynamics associated with this process are studied in detail. It is found that the frequency of the cycle increases linearly with the background rotation rate. The data show that the onset of the breakdown phase and of the reformation phase of the cycle can be characterized in terms of a local Rossby number employing an internal velocity and length scale of the jet. The critical values for this local Rossby number, for onset of breakdown and reformation, scale linearly with a global Rossby number based on the flow conditions at the source. The analysis of the experimental data in terms of relevant stability criteria suggests that the formation-breakdown cycle is due to centrifugal instability and that the temporally fluctuating axial flow plays a prominent role in the process. The development of a turbulent plume subject to background rotation was also briefly investigated by means of PIV, in order to compare its behaviour with the jets. It was revealed that unlike the jets, the plume precesses around the axis of rotation of the background. It was also observed that the mean precession frequency of the plume increases linearly with the rate of background rotation.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QA Mathematics T Technology > TA Engineering (General). Civil engineering (General)
Library of Congress Subject Headings (LCSH):	Jets -- Fluid dynamics, Plumes (Fluid dynamics), Particle image velocimetry, Turbulence, Axial flow, Rotational motion, Rossby number
Official Date:	2018
Dates:	Date Event 2018 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Chung, Yongmann M. ; Thomas, P. J. (Peter J.)
Sponsors:	Sri Lanka. University Grants Commission ; Open University of Sri Lanka ; Funds For Women Graduates
Format of File:	pdf
Extent:	xxii, 212 leaves : illustrations, charts
Language:	eng

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