Drag measurements on V-grooved surfaces on a body of revolution in axial flow

Neumann, Donald L.; Dinkelacker, A.

doi:10.1007/bf01998668

Cited by 36 publications

(17 citation statements)

References 3 publications

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“…Their results showed drag reduction peaks between 6% and 9% at dimensionless units for a groove height h + = 12 [5]. Neumann studied a V-shaped groove surface attached to a cylinder and obtained 13% drag reduction rate in a water tunnel experiment [6]. The riblets could hamper the near wall momentum exchange and delay the development of initial turbulent structures.…”

Section: Introductionmentioning

confidence: 96%

Drag reduction characteristics and flow field analysis of textured surface

Bai

Meng

et al. 2016

Friction

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A textured surface with a micro-groove structure exerts a distinct characteristic on drag reduction behavior. The fluid dynamic models of four textured surfaces are constructed in various profile geometries. Computational fluid dynamics is used to study the friction factors and drag reduction properties with various flow speeds on the textured surfaces. The friction coefficient varieties in the interface between the fluid and the textured surface are examined according to the simulation of the four geometries with V-shaped, saw tooth, rectangular, and semi-circular sections. The drag reduction efficiencies decrease with the increase in water velocity while it is less than a certain value. Moreover, the simulation results of the velocity, shear stress, energy, and turbulence effect on the V-shaped groove surface are presented in comparison with those of the smooth surface to illustrate the drag reduction mechanism. The results indicate that the peaks of the V-shaped grooves inhibit the lateral movement of the turbulent flow and generate the secondary vortex, which plays a key role in the impeding momentum exchange, thereby decreasing turbulent bursting intensity and reducing shear stress in the near-wall flow field. The kinetic energy and turbulence analysis shows that the vortex in the near-wall flow field on the textured surface is more stable compared to that on the smooth surface.

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Section: Introductionmentioning

confidence: 96%

Drag reduction characteristics and flow field analysis of textured surface

Bai

Meng

et al. 2016

Friction

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“…For example, riblets are fine rib-like surface geometries with sharp surface ridges that can be aligned either parallel or perpendicular to the flow direction and might reduce drag. A diversity of riblet shapes and sizes has been investigated experimentally and theoretically (Bechert and Bartenwerfer, 1989;Bechert et al, 2000;Bechert et al, 1997;Büttner and Schulz, 2011;Koeltzsch et al, 2002;Luchini et al, 1991;Luchini and Trombetta, 1995;Neumann and Dinkelacker, 1991), and drag reduction of stiff bodies covered with riblet material has been shown to occur (Bechert et al, 1997;Bechert et al, 1985;Dinkelacker et al, 1987). Experiments with an adjustable surface with longitudinal blade ribs and slits revealed the highest stiff-body drag reduction of 9.9%, with a groove depth of half the size of lateral riblet spacing (Bechert et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

The hydrodynamic function of shark skin and two biomimetic applications

Oeffner

Lauder

2012

Journal of Experimental Biology

260

179

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SUMMARYIt has long been suspected that the denticles on shark skin reduce hydrodynamic drag during locomotion, and a number of manmade materials have been produced that purport to use shark-skin-like surface roughness to reduce drag during swimming. But no studies to date have tested these claims of drag reduction under dynamic and controlled conditions in which the swimming speed and hydrodynamics of shark skin and skin-like materials can be quantitatively compared with those of controls lacking surface ornamentation or with surfaces in different orientations. We use a flapping foil robotic device that allows accurate determination of the self-propelled swimming (SPS) speed of both rigid and flexible membrane-like foils made of shark skin and two biomimetic models of shark skin to measure locomotor performance. We studied the SPS speed of real shark skin, a silicone riblet material with evenly spaced ridges and a Speedo ® ʻshark skin-likeʼ swimsuit fabric attached to rigid flat-plate foils and when made into flexible membrane-like foils. We found no consistent increase in swimming speed with Speedo ® fabric, a 7.2% increase with riblet material, whereas shark skin membranes (but not rigid shark skin plates) showed a mean 12.3% increase in swimming speed compared with the same skin foils after removing the denticles. Deformation of the shark skin membrane is thus crucial to the drag-reducing effect of surface denticles. Digital particle image velocimetry (DPIV) of the flow field surrounding moving shark skin foils shows that skin denticles promote enhanced leading-edge suction, which might have contributed to the observed increase in swimming speed. Shark skin denticles might thus enhance thrust, as well as reduce drag.

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“…Bechert et al [7] tested several kinds of riblets with different shapes and dimension and obtained a 5% skin friction drag reduction under a velocity of 1.3 m/s. In other experiments, Debisschop and Nieuwstadt [8] obtained a 13% drag reduction and Neumann and Dinkelacker [9] obtained 9% drag reduction of axial sample under 9 m/s. On the mechanics of drag reduction of riblets, Gallagher and Thomas [10] attributed the drag reduction to the increasing of thickness of the viscous sublayer; Choi and Orchard [11] indicated that the riblets delayed the turbulent transition; Bacher and Smith [12] and Walsh et al [13] considered that a low-speed quiet flow was retained in the valley.…”

Section: Introductionmentioning

confidence: 99%

Drag Reduction by Microvortexes in Transverse Microgrooves

Bao

Wang

Zhou

et al. 2014

Advances in Mechanical Engineering

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A transverse microgrooved surface was employed here to reduce the surface drag force by creating a slippage in bottom layer in turbulent boundary layer. A detailed simulation and experimental investigation on drag reduction by transverse microgrooves were given. The computational fluid dynamics simulation, using RNG k-turbulent model, showed that the vortexes were formed in the grooves and they were a main reason for the drag reduction. On the upside of the vortex, the revolving direction was consistent with the main flow, which decreased the flow shear stress by declining the velocity gradient. The experiments were carried out in a high-speed water tunnel with flow velocity varying from 17 to 19 m/s. The experimental results showed that the drag reduction was about 13%. Therefore, the computational and experimental results were cross-checked and consistent with each other to prove that the presented approach achieved effective drag reduction underwater.

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Drag measurements on V-grooved surfaces on a body of revolution in axial flow

Cited by 36 publications

References 3 publications

Drag reduction characteristics and flow field analysis of textured surface

Drag reduction characteristics and flow field analysis of textured surface

The hydrodynamic function of shark skin and two biomimetic applications

Drag Reduction by Microvortexes in Transverse Microgrooves

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