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Research Papers: CFD and VIV

# Sensitivity to Zone Covering of the Map of Passive Turbulence Control to Flow-Induced Motions for a Circular Cylinder at 30,000 ≤ Re ≤ 120,000

[+] Author and Article Information
Hongrae Park

Daewoo Shipbuilding and Marine
Engineering (DSME),
Seoul 04521, South Korea;
Department Naval Architecture
and Marine Engineering,
University of Michigan,
Ann Arbor, MI 48109
e-mail: hrpark@umich.edu

Eun Soo Kim

Department of Naval Architecture and
Ocean Engineering,
Pusan National University,
2 Busandaehak-ro 63beon-gil,
Jangjeon 2-dong, Geumjeong-gu,
Pusan 46241, South Korea
e-mail: bblwith@gmail.com

Michael M. Bernitsas

Mortimer E. Cooley Collegiate Professor of Naval
Architecture and Marine Engineering and
Mechanical Engineering,
University of Michigan,
Ann Arbor, MI 48109;
Vortex Hydro Energy, Inc.,
Ann Arbor, MI, 48108
e-mail: michaelb@umich.edu

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received June 15, 2016; final manuscript received October 20, 2016; published online February 13, 2017. Assoc. Editor: Ioannis K. Chatjigeorgiou.

J. Offshore Mech. Arct. Eng 139(2), 021802 (Feb 13, 2017) (6 pages) Paper No: OMAE-16-1065; doi: 10.1115/1.4035140 History: Received June 15, 2016; Revised October 20, 2016

## Abstract

Passive turbulence control (PTC) in the form of two straight roughness strips with variable width, and thickness about equal to the boundary layer thickness, is used to modify the flow-induced motions (FIM) of a rigid circular cylinder. The cylinder is supported by two end springs and the flow is in the TrSL3, high-lift, regime. The PTC-to-FIM Map, developed in the previous work, revealed zones of weak suppression (WS), strong suppression (SS), hard galloping (HG), and soft galloping (SG). In this paper, the sensitivity of the PTC-to-FIM map to: (a) the width of PTC covering, (b) PTC covering a single or multiple zones, and (c) PTC being straight or staggered is studied experimentally. Experiments are conducted in the low turbulence free surface water channel of the University of Michigan, Ann Arbor, MI. Fixed parameters are: cylinder diameter D = 8.89 cm, m* = 1.725, spring stiffness K = 763 N/m, aspect ratio l/D = 10.29, and damping ratio ζ = 0.019. Variable parameters are circumferential PTC location αPTC$∈$ (0–180 deg), Reynolds number Re $∈$ (30,000–120,000), flow velocity U$∈$ (0.36–1.45 m/s). Measured quantities are amplitude ratio A/D, frequency ratio fosc/fn,w, and synchronization range. As long as the roughness distribution is limited to remain within a zone, the width of the strips does not affect the FIM response. When multiple zones are covered, the strong suppression zone dominates the FIM.

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## Figures

Fig. 1

PTC-to-FIM Map: (a) P180 and (b) P60 [22,24]

Fig. 2

Amplitude response plot for half width with strip P180: (a) WS1, (b) HG1, (c) SG, and (d) SS

Fig. 3

Amplitude response plot for wider width with strip P180: (a) SG and (b) SS

Fig. 4

Schematic of (a) oscillator and (b) PTC cylinder

Fig. 5

Schematic of the staggered PTC cylinder model used in Sec. 4

Fig. 6

Amplitude response plot for staggered pattern with strips: (a) P60 and (b) P180

Fig. 7

Amplitude response for progressive covering

Fig. 8

Amplitude response for progressive un-covering

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