Drag reduction in pipes lined with riblets

Liu, K. N.; Christodoulou, Christiana; Riccius, O.; Joseph, Daniel D.

doi:10.2514/3.10459

Cited by 50 publications

(16 citation statements)

References 4 publications

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Section: Riblet Results and Discussionmentioning

confidence: 99%

“…In open channel, drag has been measured using water,47–51 oil,52–55 and air 39, 53, 56–64. Similarly, in closed channel flow, drag has been measured using water,47, 51, 65, 67 oil,68 and air 67, 69, 70. Both drag (for open channel) and the pressure drop (for closed channel) measurements characterize the riblet drag reduction efficiency.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fluid Drag Reduction with Shark‐Skin Riblet Inspired Microstructured Surfaces

Bixler

Bhushan

2013

Adv Funct Materials

290

189

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Engineering marvels found throughout living nature continually provide inspiration to researchers solving technical challenges. For example, skin from fast-swimming sharks intrigue researchers since its low-drag riblet microstructure is applicable to many low drag and self-cleaning (antifouling) applications. An overview of shark skin related studies that have been conducted in both open channel (external) and closed channel (internal) fl ow experiments is presented. Signifi cant work has been conducted with the open channel fl ow, and less with closed channel fl ow. The results provide design guidance when developing novel low drag and self-cleaning surfaces for applications in the medical, marine, and industrial fi elds. Experimental parameters include riblet geometry, continuous and segmented confi gurations, fl uid velocity (laminar and turbulent fl ow), fl uid viscosity (water, oil, and air), closed channel height dimensions, wettability, and scalability. The results are discussed and conceptual models are shown suggesting the effect of viscosity, coatings, and the interaction between vortices and riblet surfaces. FEATURE ARTICLEeffectively reduce drag in open and closed channel fl ow, although limited data is available with closed channel. Furthermore, closed channel experiments have been conducted to study the neighboring wall effects by using so-called microsized closed channels. In open channel, drag has been measured using water, [47][48][49][50][51] oil, [52][53][54][55] and air. [ 39 , 53 , 56-64 ] Similarly, in closed channel fl ow, drag has been measured using water, [ 47 , 51 , 65,67 ] oil, [ 68 ] and air. [ 67 , 69,70 ] Both drag (for open channel) and the pressure drop (for closed channel) measurements characterize the riblet drag reduction effi ciency.Previous experiments have utilized a variety of riblet geometries, confi gurations, materials, fl uids, and fl ow conditions (laminar and turbulent fl ow). Geometries include blade, sawtooth, scalloped, and bullnose geometries with continuous and segmented (aligned and staggered) confi gurations in water, oil, and air. Open channel oil experiments with metal riblets show drag reduction of nearly 10%, [ 52 ] whist closed channel order to catch prey. [ 40,41 , 43 ] The subsequent increased fl uid fl ow velocity at the skin reduces microorganism settlement time and promotes antifouling. [ 37,38 , 42 ] In addition, microorganisms larger than the spacing between riblets are unable to effectively adhere to and ultimately colonize the skin, which further promotes antifouling. [ 5 , 44-46 ] Low drag and antifouling surfaces have been the subject of much experimentation using shark skin riblet-inspired microtextured surfaces. An ideal surface would withstand harsh environments, adhere to a variety of substrates, combine both low drag and antifouling properties, and be relatively inexpensive.Determining the optimal riblet surface morphology for maximum drag reduction has been the focus of many efforts. Experimental results indicate that shark skin in...

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Section: Riblet Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fluid Drag Reduction with Shark‐Skin Riblet Inspired Microstructured Surfaces

Bixler

Bhushan

2013

Adv Funct Materials

290

189

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show abstract

“…Riblets typically consist of closely spaced structures, such as triangular grooves or blades, in the cross-stream direction that are uniform in the streamwise direction of the flow [16]. The unique characteristic of riblets is that they induce a drag reduction instead of a drag increase for a range of Reynolds numbers determined by the square-root of the groove cross-section of the riblets [17,18].…”

Section: Introductionmentioning

confidence: 99%

Influence of Surface Anisotropy on Turbulent Flow Over Irregular Roughness

Busse

Jelly

2019

Flow Turbulence Combust

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The influence of surface anisotropy upon the near-wall region of a rough-wall turbulent channel flow is investigated using direct numerical simulation (DNS). A set of nine irregular rough surfaces with fixed mean peak-to-valley height, near-Gaussian height distributions and specified streamwise and spanwise correlation lengths were synthesised using a surface generation algorithm. By defining the surface anisotropy ratio (SAR) as the ratio of the streamwise and spanwise correlation lengths of the surface, we demonstrate that surfaces with a strong spanwise anisotropy (SAR <1) can induce an over 200% increase in the roughness function ΔU + , compared to their streamwise anisotropic (SAR >1) equivalent. Furthermore, we find that the relationship between the roughness function ΔU + and the SAR parameter approximately follows an exponentially decaying function. The statistical response of the near-wall flow is studied using a "double-averaging" methodology in order to distinguish form-induced "dispersive" stresses from their turbulent counterparts. Outer-layer similarity is recovered for the mean velocity defect profile as well as the Reynolds stresses. The dispersive stresses all attain their maxima within the roughness canopy. Only the streamwise dispersive stress reaches levels that are comparable to the equivalent Reynolds stress, with surfaces of high SAR attaining the highest levels of streamwise dispersive stress. The Reynolds stress anisotropy also shows distinct differences between cases with strong streamwise anisotropy that stay close to an axisymmetric, rodlike state for all wall-normal locations, compared to cases with spanwise anisotropy where an axisymmetric, disk-like state of the Reynolds stress anisotropy tensor is observed around the roughness mean plane. Overall, the results from this study underline that the drag penalty incurred by a rough surface is strongly influenced by the surface topography and highlight its impact upon the mean momentum deficit in the outer flow as well as the Reynolds and dispersive stresses within the roughness layer.

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“…4 Inspired by the shape of the ribs on the shark denticles, various approaches to drag reduction using riblet surfaces have been introduced and previously investigated, with a variety of riblet shapes such as V-grooves, U-grooves, and rectangular upright knifeedge structures all deployed in laminar flows, 5-8 turbulent channel flows, 1,[9][10][11][12][13][14][15] and boundary layers, [16][17][18][19] as well as in high Mach number flows, [20][21][22] and pipe flows. [23][24][25] Bio-inspired riblet tapes have also previously been applied to the hull of the Stars and Stripes yacht in the 1987 America's Cup tournament and were also used by the ORACLE Team USA (previously known as BMW ORA-CLE team) in the 2010 America's Cup tournament, resulting in a win in both cases. 15,26 A High Speed Buoyancy Propelled Vehicle (HSBPV) known as MOBY-D of length 12.6 m and diameter of 3.35 m was also tested in water with a riblet surface (35% surface coverage) resulting in 3.4% reduction in the skin friction drag.…”

Section: Introductionmentioning

confidence: 99%

Geometric optimization of riblet-textured surfaces for drag reduction in laminar boundary layer flows

Raayai-Ardakani

McKinley

2019

Physics of Fluids

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Micro-scale riblets are shown to systematically modify viscous skin friction in laminar flows at high Reynolds numbers. The textured denticles of native sharkskin are widely cited as a natural example of this passive drag reduction mechanism. Since the structure of a viscous boundary layer evolves along the plate, the local frictional drag changes are known empirically to be a function of the length of the plate in the flow direction, as well as the riblet spacing, and the ratio of the height to spacing of the riblets. Here, we aim to establish a canonical theory for high Reynolds number laminar flow over V-groove riblets to explore the self-similarity of the velocity profiles and the evolution of the total frictional drag exerted on plates of different lengths. Scaling analysis, conformal mapping, and numerical calculations are combined to show that the potential drag reduction achieved using riblet surfaces depends on an appropriately rescaled form of the Reynolds number and on the aspect ratio of the riblets (defined in terms of the ratio of the height to spacing of the texture). We show that riblet surfaces require a scaled Reynolds number lower than a maximum threshold to be drag-reducing and that the change in drag is a nonmonotonic function of the aspect ratio of the riblet texture. This physical scaling and the computational results presented here can be used to explain the underlying physical mechanism of this mode of passive drag reduction to rationalize the geometric dimensions of shark denticles, as well as the results of experiments with shark denticle replicas of various sizes, and guide designs for optimizing the textural parameters that result in friction-reducing surfaces.

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Drag reduction in pipes lined with riblets

Cited by 50 publications

References 4 publications

Fluid Drag Reduction with Shark‐Skin Riblet Inspired Microstructured Surfaces

Fluid Drag Reduction with Shark‐Skin Riblet Inspired Microstructured Surfaces

Influence of Surface Anisotropy on Turbulent Flow Over Irregular Roughness

Geometric optimization of riblet-textured surfaces for drag reduction in laminar boundary layer flows

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