scholarly journals Bioinspired surfaces for turbulent drag reduction

2016 ◽  
Vol 374 (2073) ◽  
pp. 20160189 ◽  
Author(s):  
Kevin B. Golovin ◽  
James W. Gose ◽  
Marc Perlin ◽  
Steven L. Ceccio ◽  
Anish Tuteja
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Scaling Laws ◽  
Experimental Studies ◽  
Roughness Effects ◽  
Structured Surfaces ◽  
Turbulent Drag ◽  
Capillary Resistance ◽  
Flow Turbulence ◽  
Friction Drag Reduction

In this review, we discuss how superhydrophobic surfaces (SHSs) can provide friction drag reduction in turbulent flow. Whereas biomimetic SHSs are known to reduce drag in laminar flow, turbulence adds many new challenges. We first provide an overview on designing SHSs, and how these surfaces can cause slip in the laminar regime. We then discuss recent studies evaluating drag on SHSs in turbulent flow, both computationally and experimentally. The effects of streamwise and spanwise slip for canonical, structured surfaces are well characterized by direct numerical simulations, and several experimental studies have validated these results. However, the complex and hierarchical textures of scalable SHSs that can be applied over large areas generate additional complications. Many studies on such surfaces have measured no drag reduction, or even a drag increase in turbulent flow. We discuss how surface wettability, roughness effects and some newly found scaling laws can help explain these varied results. Overall, we discuss how, to effectively reduce drag in turbulent flow, an SHS should have: preferentially streamwise-aligned features to enhance favourable slip, a capillary resistance of the order of megapascals, and a roughness no larger than 0.5, when non-dimensionalized by the viscous length scale. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’.

Turbulent flow drag reduction and degradation with dilute polymer solutions

1970 ◽  
Vol 43 (4) ◽  
pp. 689-710 ◽  
Author(s):  
R. W. Paterson ◽  
F. H. Abernathy
Keyword(s):  
Molecular Weight ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Average Molecular Weight ◽  
Experimental Studies ◽  
Polymer Degradation ◽  
High Viscosity ◽  
Turbulent Pipe Flow ◽  
Shear Stresses ◽  
Flow Drag

Experimental studies of drag reduction and polymer degradation in turbulent pipe flow with dilute water solutions of unfractionated polyethylene oxide are described. Drag reduction results indicate that the magnitude of the reduction cannot be correlated on the basis of weight average molecular weight, rather the phenomenon depends strongly on the concentration of the highest molecular weight species present in the molecular weight distribution. Polymer degradation in turbulent flow is found to be severe for high molecular weight polymers causing appreciable changes in drag reduction and molecular weight with the duration of flow. Data indicates that drag reduction exists in the limit of infinite dilution suggesting that the phenomenon is due to the interaction of individual polymer molecules with the surrounding solvent and that the extent of reduction is relatively independent of pipe diameter when a comparison is carried out at equal solvent wall shear stresses. Consideration of the high viscosity obtained with solutions in an irrotational laminar flow field suggests this is due to polymer molecule deformation and that this phenomenon is central to the mechanism of turbulent flow drag reduction.

COMPUTATIONAL AND EXPERIMENTAL STUDIES OF AN ACTIVE SKIN FOR TURBULENT DRAG REDUCTION

2002 ◽  
Author(s):  
Othon Rediniotis ◽  
Dimitris Lagoudas ◽  
Raghavendran Mani ◽  
Lance Traub ◽  
George Karniadakis ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Experimental Studies ◽  
Turbulent Drag Reduction ◽  
Turbulent Drag

scholarly journals Analysis of Shark Skin Riblet Surfaces for Fluid Drag Reduction in Turbulent Flow Regime

2019 ◽  
Vol 9 (1S4) ◽  
pp. 666-668
Keyword(s):  
Fluid Flow ◽  
Flow Field ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Flow System ◽  
Shark Skin ◽  
Structured Surfaces ◽  
Turbulent Flow Regime ◽  
Fluid Drag ◽  
Fluid Drag Reduction

: The integument of fast swimming shark exhibits riblet inspired micro- structured surfaces oriented in the path of flow that will help to make lesser the wall drag in the tempestuous-flow system (turbulent flow). Design have been made for study and utilization, that has been recreate and refine as same as of the shark-skin riblets, presuming an extreme drag depletion of nearly 10% (percent). Mechanism of fluid drag in tempestuous flow and riblet drag depletion theories from experiments and simulations are examined. An examination of riblet intrepratation are discussed and the stellar riblet sizes are defined. An assessment of studies experimenting with riblets-topped shark scale replicas is also discussed. A method for preferring stellar riblet dimensions based on fluid-flow attributes is briefed and current manufacturing approaches are summarized. Due to the existence of little amounts of mucus/booger membranes on the integument of the shark, it is presumed that the constrained application of aqua phobic materials will recast the flow field around the riblets in some way favorable to the goals of augmented drag depletion

Substantial drag reduction in turbulent flow using liquid-infused surfaces

2017 ◽  
Vol 827 ◽  
pp. 448-456 ◽  
Author(s):  
Tyler Van Buren ◽  
Alexander J. Smits
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Couette Flow ◽  
Viscosity Ratio ◽  
Area Fraction ◽  
Groove Width ◽  
Test Surface ◽  
Test Liquid ◽  
Turbulent Drag

Experiments are presented that demonstrate how liquid-infused surfaces can reduce turbulent drag significantly in Taylor–Couette flow. The test liquid was water, and the test surface was composed of square microscopic grooves measuring $100~\unicode[STIX]{x03BC}\text{m}$ to $800~\unicode[STIX]{x03BC}\text{m}$, filled with alkane liquids with viscosities from 0.3 to 1.4 times that of water. We achieve drag reduction exceeding 35 %, four times higher than previously reported for liquid-infused surfaces in turbulent flow. The level of drag reduction increased with viscosity ratio, groove width, fluid area fraction and Reynolds number. The optimum groove width was given by $w^{+}\approx 35$.

scholarly journals Friction-Drag Reduction by Transverse Wall Motion – A Review

2020 ◽  
Vol 36 (5) ◽  
pp. 649-663
Author(s):  
Michael A. Leschziner
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Wall Motion ◽  
Experimental Studies ◽  
Wall Turbulence ◽  
Civil Aviation ◽  
Turbulent Friction ◽  
Entry Level ◽  
Major Interest ◽  
Friction Drag Reduction

ABSTRACTThe quest for drag reduction is driven by environmental concerns, in general, and the need to reduce fuel consumption in transport applications, in particular. Turbulent friction is especially important in civil aviation, accounting for over 50% of the total drag in cruise. In this context, spatially and/or temporally varying in-plane wall motion, while undoubtedly difficult to implement in practice, has attracted major interest, because of the large drag-reduction margins it yields. It is also a forcing method that is of fundamental interest, as it provokes intriguing interactions between the spanwise Stokes layer induced by the wall motion and the near-wall turbulence-regeneration mechanisms. This article provides a relatively brief, ‘entry-level’, review of research in this area, principally over the past two decades. While far from being exhaustive, the review conveys a reasonably detailed picture of some major physical issues as well as of the outcome of the most important computational and experimental studies. Particular emphasis is placed on the question of how results obtained in idealised laboratory conditions and by simulation at relatively low Reynolds-number values pertain to high values typical of high-speed transport.

Liquid-infused surfaces as a passive method of turbulent drag reduction

2017 ◽  
Vol 824 ◽  
pp. 688-700 ◽  
Author(s):  
M. K. Fu ◽  
I. Arenas ◽  
S. Leonardi ◽  
M. Hultmark
Keyword(s):  
Drag Reduction ◽  
Turbulent Flows ◽  
Experimental Studies ◽  
Turbulent Channel Flow ◽  
Superhydrophobic Surfaces ◽  
Fluid Interfaces ◽  
Turbulent Drag Reduction ◽  
Liquid Lubricant ◽  
Passive Method ◽  
Turbulent Drag

Liquid-infused surfaces present a novel, passive method of turbulent drag reduction. Inspired by the Nepenthes Pitcher Plant, liquid-infused surfaces utilize a lubricating fluid trapped within structured roughness to facilitate a slip at the effective surface. The conceptual idea is similar to that of superhydrophobic surfaces, which rely on a lubricating air layer, whereas liquid-infused surfaces use a preferentially wetting liquid lubricant to create localized fluid–fluid interfaces. Maintaining the presence of these slipping interfaces has been shown to be an effective method of passively reducing skin friction drag in turbulent flows. Given that liquid-infused surfaces have only recently been considered for drag reduction applications, there is no available framework to relate surface and lubricant characteristics to any resulting drag reduction. Here we use results from direct numerical simulations of turbulent channel flow over idealized, liquid-infused grooves to demonstrate that the drag reduction achieved using liquid-infused surfaces can be described using the framework established for superhydrophobic surfaces. These insights can be used to explain drag reduction results observed in experimental studies of lubricant-infused surfaces. We also demonstrate how a liquid-infused surface can reduce drag even when the viscosity of the lubricant exceeds that of the external fluid flow, which at first glance can seem counter-intuitive.

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