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Research Papers: CFD and VIV

Selective Surface Roughness to Suppress Flow-Induced Motion of Two Circular Cylinders at 30,000 < Re < 120,000

[+] Author and Article Information
Hongrae Park

Department of Naval Architecture
and Marine Engineering,
University of Michigan,
Ann Arbor, MI 48105
e-mail: hrpark@umich.edu

Michael M. Bernitsas

Professor
Department of Naval Architecture
and Marine Engineering,
University of Michigan,
Ann Arbor, MI 48105
e-mail: michaelb@umich.edu

Eun Soo Kim

Department of Naval Architecture
and Marine Engineering,
University of Michigan,
Ann Arbor, MI 48105
e-mail: bblwith@umich.edu

1Present address: Daewoo Shipbuilding and Marine Engineering (DSME), Seoul, South Korea.

2Present address: Mechanical Engineering; and CTO of Vortex Hydro Energy, Dexter, MI.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received July 5, 2013; final manuscript received July 18, 2014; published online August 13, 2014. Assoc. Editor: Longbin Tao.

J. Offshore Mech. Arct. Eng 136(4), 041804 (Aug 13, 2014) (6 pages) Paper No: OMAE-13-1067; doi: 10.1115/1.4028061 History: Received July 05, 2013; Revised July 18, 2014

In the Marine Renewable Energy Laboratory of the University of Michigan, selectively located surface roughness has been designed successfully to suppress vortex-induced vibrations (VIV) of a single cylinder by 60% compared to a smooth cylinder. In this paper, suppression of flow-induced motions of two cylinders in tandem using surface roughness is studied experimentally by varying flow velocity and cylinder center-to-center spacing. Two identical rigid cylinders suspended by springs with their axes perpendicular to the flow are allowed one degree of freedom motion transverse to the flow direction. Surface roughness is applied in the form of four roughness strips helically placed around the cylinder. Results are compared to smooth cylinders also tested in this work. Amplitude ratio A/D, frequency ratio fosc/fn,water, and range of synchronization are measured. Regardless of the center-to-center cylinder distance, the amplitude response of the upstream smooth cylinder is similar to that of an isolated smooth cylinder. The wake from the upstream cylinder with roughness is narrower and longer and has significant influence on the amplitude of the downstream cylinder. The latter is reduced in the initial and upper branches while its range of VIV-synchronization is extended. Galloping is suppressed in both cylinders. In addition, the amplitude of the upstream rough cylinder and its range of synchronization increase with respect to the isolated rough cylinder.

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References

Figures

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Fig. 1

Schematic of two oscillating cylinders in tandem

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Fig. 2

Picture of PTC-cylinder with four helical strips

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Fig. 3

Amplitude response plots for two smooth cylinders: (a) upstream cylinder and (b) downstream cylinder

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Fig. 4

Frequency response plots for two smooth cylinders: (a) upstream cylinder and (b) downstream cylinder

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Fig. 5

Amplitude response plots for two PTC-cylinders: (a) upstream cylinder and (b) downstream cylinder

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Fig. 6

Wake of upstream cylinder at U* = 13.5: (a) smooth cylinder and (b) PTC-cylinder

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Fig. 8

Power spectra of displacement at U* = 7.47 in the upper branch: (a) upstream cylinder and (b) downstream cylinder

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Fig. 7

Frequency response plots for two PTC-cylinders: (a) upstream cylinder and (b) downstream cylinder

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