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Research Papers: Fluid-Structure Interaction

Aeroacoustic Response of a Single Cylinder With Straight Circular Fins in Cross-Flow

[+] Author and Article Information
Nadim Arafa

Faculty of Engineering and Applied Science,
University of Ontario Institute of Technology,
2000 Simcoe Street North,
Oshawa, ON L1H7K4, Canada
e-mail: nadim.arafa@uoit.ca

Atef Mohany

Faculty of Engineering and Applied Science,
University of Ontario Institute of Technology,
2000 Simcoe Street North,
Oshawa, ON L1H7K4, Canada
e-mail: atef.mohany@uoit.ca

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received September 10, 2014; final manuscript received January 9, 2015; published online February 24, 2015. Assoc. Editor: Jong Chull Jo.

J. Pressure Vessel Technol 137(5), 051301 (Oct 01, 2015) (8 pages) Paper No: PVT-14-1147; doi: 10.1115/1.4029658 History: Received September 10, 2014; Revised January 09, 2015; Online February 24, 2015

The phenomenon of sound generation has been investigated in some detail for the case of bare cylinders; however, the effect of adding fins to the cylinder on the flow–sound interaction mechanism is not yet fully understood. Thus, the aeroacoustic response of a cylinder with straight circular fins in cross-flow is investigated experimentally in this work. During the experiments, the acoustic modes of the duct housing the cylinder are self-excited due to the vortex shedding that emerges from the cylinder's surface. In order to determine the effect of different fin parameters on the onset and intensity of acoustic resonance, 14 different finned cylinders with fin thickness ranging from 0.35 to 1.5 mm and fin density ranging from 4 to 13.7 fin/in. are investigated. It is observed that the finned cylinders experience an earlier acoustic resonance and higher levels of acoustic pressure compared to their equivalent bare cylinders. Moreover, it is observed that, for constant fin spacing, the acoustic pressure amplitude increases and the acoustic resonance occurs at earlier velocities as the fin thickness increases. On the other hand, for constant fin thickness, as the fin spacing increases the amplitude of the acoustic pressure decreases while the onset of the resonance is delayed. Finally, the effect of the cylinder's aspect ratio on the acoustic resonance excitation is presented. It is shown that as the finned cylinders' aspect ratio increases from 4.85 to 11.3, the normalized acoustic pressure during resonance increases drastically. However, for bare cylinders the normalized acoustic pressure during resonance is not highly dependent on the cylinders' aspect ratio. These results indicate that adding fins to the cylinder alters the flow field downstream of the cylinder in a manner that makes it more susceptible to acoustic excitation.

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Figures

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Fig. 1

Schematic drawing of the experimental setup showing the acoustic particle velocity and acoustic pressure distribution for the first acoustic cross-mode along with the location of the microphone relative to the cylinder

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Fig. 2

Detailed drawing of the straight finned cylinder showing the fin parameters

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Fig. 3

Waterfall plot of acoustic pressure spectra versus the flow velocity for a single bare cylinder in cross-flow, D = 12.7 mm

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Fig. 4

Aeroacoustic response of single bare cylinder in cross-flow, D = 12.7 mm

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Fig. 5

Aeroacoustic response of a single finned cylinder (SF1), t = 1.5 mm, s = 1.5 mm, and De = 19 mm

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Fig. 6

Comparison of the normalized acoustic pressure of a straight finned cylinder (SF1) and a bare cylinder with a diameter equal to its effective diameter

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Fig. 7

The pressure drop versus the Mach number for finned cylinder and its equivalent bare cylinder

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Fig. 8

Comparison of the normalized acoustic pressure of straight finned cylinders showing the effect of the fin thickness along with the response of a bare cylinder with the same root diameter as that of the finned cylinders (D = 12.7 mm). The fin spacing is (a) 1.5 mm, (b) 2 mm, and (c) 2.5 mm.

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Fig. 9

Comparison of the normalized acoustic pressure of straight finned cylinders showing the effect of the fin spacing. The fin thickness is (a) is 1.5 mm and (b) 0.381 mm.

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Fig. 10

Comparison of the normalized acoustic pressure of straight finned cylinders having variable fin thickness and fin spacing. The fin density is 8.47 fins/in. for all of the cylinders.

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Fig. 11

Comparison of the aeroacoustic response of bare and finned cylinders for the current work against that of Eid and Ziada [20]

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Fig. 12

Comparison of the aeroacoustic response of straight finned cylinder, SF13, obtained in three different test sections, l/D is the aspect ratio of the cylinder, D = De = 15.7 mm

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Fig. 13

Comparison of the aeroacoustic response of bare cylinder, D = 25.4 mm, obtained in three different test sections

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