The turbulent wake of two side-by-side circular cylinders

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The turbulent wake of two side-by-side circular cylinders

 

Author: Yiu, Man-wah
Title: The turbulent wake of two side-by-side circular cylinders
Degree: M.Sc.
Year: 2000
Subject: Turbulence
Cylinders
Heat -- Transmission
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Mechanical Engineering
Pages: vi, 107 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1532195
URI: http://theses.lib.polyu.edu.hk/handle/200/2790
Abstract: This work aims to study experimentally the turbulent heat and momentum transport in the wake of two side-by-side circular cylinders. Spacing T between the cylinder axes was varied from 1.5d to 3d (d is the cylinder diameter). Both cylinders were slightly heated. While a movable three-wire probe was used to measure the velocity and temperature fluctuations, another X-wire was used to provide a phase reference. Measurements were conducted at x/d =10, 20 and 40 at a Reynolds number of 5830 (based on the free stream velocity U∞). At T/d =1.5, the phase-averaged velocity and temperature fields display a single vortex street and is asymmetrical in terms of topology with respect to the flow centreline. The two rows of vortices exhibit a great difference in strength. The vortices of greater strength play a dominant role in momentum and scalar heat transport. At T/d =3.0, two in-phase vortex streets occur initially, but merge into one by x/d = 40. The vorticity flux density indicates that, while the outer vortex interacts largely with the adjacent oppositely signed inner vortices located near the flow centreline, the inner vortex interacts with the cross-stream inner vortices as well as with adjacent outer vortices. As a result, vorticity associated with the inner vortex is 'neutralised' quicker than that associated with the outer vortex, leading to the early disappearance of inner vortices and the formation of a single vortex street. It is further found that both inner and outer vortices can transport momentum efficiently, but the inner vortices do not seem to play a significant role in scalar heat transport, probably because of their relatively weak strength.

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