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Selective roughness in the boundary layer to suppress flow-induced motions of circular cylinder at 30,000

Publication Type : Conference Paper

Publisher : OMAE

Source : Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, Volume 7, Rotterdam, p.715-724 (2011)

Url :

ISBN : 9780791844397

Keywords : Arctic engineering, Atmospheric thermodynamics, Boundary layer thickness, Boundary layers, Circular cylinders, Complex flow structures, Cylinder surface, Field of views, Flow regimes, Flow-induced motion, Frequency measurements, Gradual modifications, Maximum amplitude, Passive control, Respiratory mechanics, Suppression devices, turbulence, Turbulence controls, University of Michigan, Visualization

Campus : Amritapuri

School : School of Engineering

Department : Mechanical Engineering

Year : 2011

Abstract : A passive control means to suppress flow-induced motions (FIM) of a rigid circular cylinder in the TrSL3, high-lift, flow regime is formulated and tested experimentally. The developed method uses passive turbulence control (PTC) consisting of selectively located roughness on the cylinder surface with thickness about equal to the boundary layer thickness. The map of “PTC-to-FIM,” developed in previous work, revealed robust zones of weak suppression, strong suppression, hard galloping, and soft galloping. PTC has been used successfully to enhance FIM for hydrokinetic energy harnessing using the VIVACE Converter. PTC also revealed the potential to suppress FIM to various levels. The map is flow-direction dependent. In this paper, the “PTC-to-FIM” map is used to guide development of FIM suppression devices that are flow-direction independent and hardly affect cylinder geometry. Experiments are conducted in the Low Turbulence Free Surface Water Channel of the University of Michigan on a rigid, horizontal, circular cylinder, suspended on springs. Amplitude and frequency measurements and broad field-of-view visualization reveal complex flow structures and their relation to suppression. Several PTC designs are tested to understand the effect of PTC roughness, location, coverage, and configuration. Gradual modification of PTC parameters, leads to improved suppression and evolution of a design reducing the VIV synchronization range. Over a wide range of high reduced velocities, VIV is fully suppressed. The maximum amplitude occurring near the system’s natural frequency is reduced by about 63% compared to the maximum amplitude of the smooth cylinder.

Cite this Research Publication : Ha Park, Bernitsas, M. Mab c, and Kumar, R. Abd, “Selective roughness in the boundary layer to suppress flow-induced motions of circular cylinder at 30,000

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