Reduction of Bluff-Body Drag and Suppression of Vortex Shedding by the Introduction of Wavy Separation Lines

Bearman, P. W.; Owen, J. J. T.

doi:10.1006/jfls.1997.0128

Cited by 199 publications

(102 citation statements)

References 6 publications

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“…Vortex-induced vibrations and strategies to reduce them have been the subject of extensive studies in engineering (Bearman and Owen, 1998;Owen et al, 2001;Owen et al, 2000;Scruton, 1965;Williamson and Govardhan, 2004;Williamson and Govardhan, 2008;Zdravkovich, 1981). Much of the recent interest originates from offshore industries (Bearman, 2009).…”

Section: Vortex Suppression By Wavy Surfacesmentioning

confidence: 99%

Harbor seal vibrissa morphology suppresses vortex-induced vibrations

Hanke

Witte

Miersch

et al. 2010

Journal of Experimental Biology

193

273

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SUMMARYHarbor seals (Phoca vitulina) often live in dark and turbid waters, where their mystacial vibrissae, or whiskers, play an important role in orientation. Besides detecting and discriminating objects by direct touch, harbor seals use their whiskers to analyze water movements, for example those generated by prey fish or by conspecifics. Even the weak water movements left behind by objects that have passed by earlier can be sensed and followed accurately (hydrodynamic trail following). While scanning the water for these hydrodynamic signals at a swimming speed in the order of meters per second, the seal keeps its long and flexible whiskers in an abducted position, largely perpendicular to the swimming direction. Remarkably, the whiskers of harbor seals possess a specialized undulated surface structure, the function of which was, up to now, unknown. Here, we show that this structure effectively changes the vortex street behind the whiskers and reduces the vibrations that would otherwise be induced by the shedding of vortices from the whiskers (vortex-induced vibrations). Using force measurements, flow measurements and numerical simulations, we find that the dynamic forces on harbor seal whiskers are, by at least an order of magnitude, lower than those on sea lion (Zalophus californianus) whiskers, which do not share the undulated structure. The results are discussed in the light of pinniped sensory biology and potential biomimetic applications. Supplementary material available online at

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Section: Vortex Suppression By Wavy Surfacesmentioning

confidence: 99%

Harbor seal vibrissa morphology suppresses vortex-induced vibrations

Hanke

Witte

Miersch

et al. 2010

Journal of Experimental Biology

193

273

View full text Add to dashboard Cite

show abstract

“…Owing to the slight angle at which these paddles were drawn through the water, the occurring vortices spread slowly laterally in one branch from the paddles. Because of the undulated shape, vortices probably interacted and partly extinguished each other after generation (Bearman and Owen, 1998) (see also Hanke et al, 2010).…”

Section: Stimulus Characterizationmentioning

confidence: 99%

Hydrodynamic discrimination of wakes caused by objects of different size or shape in a harbour seal (Phoca vitulina)

Wieskotten

Mauck

Miersch

et al. 2011

Journal of Experimental Biology

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SUMMARYHarbour seals can use their mystacial vibrissae to detect and track hydrodynamic wakes. We investigated the ability of a harbour seal to discriminate objects of different size or shape by their hydrodynamic signature and used particle image velocimetry to identify the hydrodynamic parameters that a seal may be using to do so. Hydrodynamic trails were generated by different sized or shaped paddles that were moved in the calm water of an experimental box to produce a characteristic signal. In a twoalternative forced-choice procedure the blindfolded subject was able to discriminate size differences of down to 3.6cm (Weber fraction 0.6) when paddles were moved at the same speed. Furthermore the subject distinguished hydrodynamic signals generated by flat, cylindrical, triangular or undulated paddles of the same width. Particle image velocimetry measurements demonstrated that the seal could have used the highest velocities and the steepness of the gradients within the wake to discriminate object size, beside the size of counter-rotating vortices and the spatial extension of a wake. For shape discrimination the subject could have used the spatial extension of the whole wake, in addition to the arrangement of the vortices. We tested whether the seal used highest velocities, the steepness of the gradients and the spatial extension of the wake in a second set of experiments by varying moving speed and paddle size, respectively. The subject was still able to discriminate between the respective object sizes, but the minimum detectable size difference increased to 4.4cm (Weber fraction 3.6). For the shape discrimination task, the seal was only able to distinguish flat from triangular paddles. Our results indicate that the seal's discrimination abilities depend on more than one hydrodynamic parameter.

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“…VIV may cause serious fatigue damageon the structures in offshore engineering. Much research work has been done on this typical fluid-structure interaction phenomenon throughout centuries, both numerically and experimentally, toward the understanding of the dynamic response features of VIV (Naudascher, 1987;Sarpkaya, 2004;Gabbai and Benaroya, 2005;Williamson and Govardhan, 2008;Wu et al, 2012b;Fan et al, 2015) and the VIV suppression (Zdravkovich, 1981;Bearman and Owen, 1998;Galvao et al, 2008;Assi et al, 2009;Wu et al, 2012a;Huera-Huarte, 2014;Gao et al, 2015aGao et al, , 2015bGao et al, , 2016.…”

Section: Introductionmentioning

confidence: 99%

Influences of the helical strake cross-section shape on vortex-induced vibrations suppression for a long flexible cylinder

Luan

Liu

et al. 2017

China Ocean Eng

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An experimental study on a bare flexible cylinder as well as cylinders fitted with two types of cross-sectioned helical strakes was carried out in a towing tank. The main purpose of this paper is to investigate the effects of strakes' crosssection on the vortex-induced vibrations (VIV) suppression of a flexible cylinder. The square-sectioned and roundsectioned helical strakes were selected in the experimental tests. The uniform current was generated by towing the cylinder models along the tank using a towing carriage. The Reynolds number was in the range of 800-16000. The strain responses were measured by the strain gages in cross-flow (CF) and in-line (IL) directions. A modal analysis method was adopted to obtain the displacement responses using the strain signals in different measurement positions. The comparison of the experimental results among the bare cylinder, square-sectioned straked cylinder and roundsectioned straked cylinder was performed. The helical strakes can effectively reduce the strain amplitude, displacement amplitude, response frequencies and dominant modes of a flexible cylinder excited by VIV. And the mean drag coefficients of straked cylinders were approximately consistent with each other. In addition, the squaresectioned and round-sectioned strakes nearly share the similar VIV reduction behaviors. Sometimes, the strakes with round-section represent more excellent effects on the VIV suppression of response frequency than those with squaresection.

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Reduction of Bluff-Body Drag and Suppression of Vortex Shedding by the Introduction of Wavy Separation Lines

Cited by 199 publications

References 6 publications

Harbor seal vibrissa morphology suppresses vortex-induced vibrations

Harbor seal vibrissa morphology suppresses vortex-induced vibrations

Hydrodynamic discrimination of wakes caused by objects of different size or shape in a harbour seal (Phoca vitulina)

Influences of the helical strake cross-section shape on vortex-induced vibrations suppression for a long flexible cylinder

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