Drag reduction in ultrahydrophobic channels with micro-nano structured surfaces

2010 ◽  
Vol 53 (7) ◽  
pp. 1298-1305 ◽  
Author(s):  
Si Lu ◽  
ZhaoHui Yao ◽  
PengFei Hao ◽  
ChengSong Fu
Keyword(s):  
Drag Reduction ◽  
Structured Surfaces

scholarly journals Discovery of riblets in a bird beak ( Rynchops ) for low fluid drag

2016 ◽  
Vol 374 (2073) ◽  
pp. 20160134 ◽  
Author(s):  
Samuel Martin ◽  
Bharat Bhushan
Keyword(s):  
Pressure Drop ◽  
Drag Reduction ◽  
Shear Stresses ◽  
Structured Surfaces ◽  
Mako Shark ◽  
Fluid Drag ◽  
Bird Beak ◽  
Modelling Studies ◽  
Flow Pressure ◽  
First Time

Riblet structures found on fast-swimming shark scales, such as those found on a mako shark, have been shown to reduce fluid drag. In previous experimental and modelling studies, riblets have been shown to provide drag reduction by lifting vortices formed in turbulent flow, decreasing overall shear stresses. Skimmer birds ( Rynchops ) are the only birds to catch fish in flight by flying just above the water surface with a submerged beak to fish for food. Because they need to quickly catch prey, reducing drag on their beak is advantageous. For the first time, riblet structures found on the beak of the skimmer bird have been studied experimentally and computationally for low fluid drag properties. In this study, skimmer replicas were studied for drag reduction through pressure drop in closed-channel, turbulent water flow. Pressure drop measurements are compared for black and yellow skimmer beaks in two configurations, and mako shark skin. In addition, two configurations of skimmer beak were modelled to compare drag properties and vortex structures. Results are discussed, and a conceptual model is presented to explain a possible drag reduction mechanism in skimmers. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’.

Microstructured Surfaces for Drag Reduction Purposes: Experiments and Simulations on Rectangular 2D Riblets

2005 ◽  
Vol 899 ◽  
Author(s):  
Håkan Rapp ◽  
Igor Zoric ◽  
Bengt Kasemo
Keyword(s):  
Drag Reduction ◽  
Plane Channel ◽  
Viscous Sublayer ◽  
Friction Drag ◽  
Frictional Drag ◽  
Navier Stokes Equation ◽  
Number Range ◽  
Structured Surfaces ◽  
Structured Surface ◽  
Wall Unit

AbstractIt is well established that properly structured surface exhibits a lower friction drag, when exposed to a turbulent boundary layer, than a smooth surface under the same flow conditions. The observed drag decrease is usually attributed to an increased thickness of the viscous sublayer. In this work we examine the friction drag reducing mechanism. Two parallel approaches towards achieving this goal are presented. Photolithography was used to manufacture rectangular riblets in the 10∝m range on a standard 4” silicon wafer. A special compact plane channel system was designed and used for measurements of the frictional drag on structured surfaces in the turbulent flow covering a wide Reynolds number range. Navier-Stokes equation, for the examined drag reducing geometry, was solved in the laminar regime with appropriate boundary conditions. The resulting velocity field was used to extract the protrusion heights difference for streamwise and spanwise flows over the structured surface. The latter was then related to the experimentally measured drag reduction slope. We show that in case of a rectangular riblet, with a size of the order of one wall unit, the observed drag reduction can be accounted for within the above model.

scholarly journals Superhydrophobic hierarchically structured surfaces in biology: evolution, structural principles and biomimetic applications

2016 ◽  
Vol 374 (2073) ◽  
pp. 20160191 ◽  
Author(s):  
W. Barthlott ◽  
M. Mail ◽  
C. Neinhuis
Keyword(s):  
Drag Reduction ◽  
Self Assembly ◽  
Phylogenetic Trees ◽  
Electron Microscopic ◽  
Lotus Effect ◽  
Structured Surfaces ◽  
Biomimetic Surfaces ◽  
Key Innovation ◽  
Extant Species ◽  
Self Cleaning

A comprehensive survey of the construction principles and occurrences of superhydrophobic surfaces in plants, animals and other organisms is provided and is based on our own scanning electron microscopic examinations of almost 20 000 different species and the existing literature. Properties such as self-cleaning (lotus effect), fluid drag reduction (Salvinia effect) and the introduction of new functions (air layers as sensory systems) are described and biomimetic applications are discussed: self-cleaning is established, drag reduction becomes increasingly important, and novel air-retaining grid technology is introduced. Surprisingly, no evidence for lasting superhydrophobicity in non-biological surfaces exists (except technical materials). Phylogenetic trees indicate that superhydrophobicity evolved as a consequence of the conquest of land about 450 million years ago and may be a key innovation in the evolution of terrestrial life. The approximate 10 million extant species exhibit a stunning diversity of materials and structures, many of which are formed by self-assembly, and are solely based on a limited number of molecules. A short historical survey shows that bionics (today often called biomimetics) dates back more than 100 years. Statistical data illustrate that the interest in biomimetic surfaces is much younger still. Superhydrophobicity caught the attention of scientists only after the extreme superhydrophobicity of lotus leaves was published in 1997. Regrettably, parabionic products play an increasing role in marketing. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’.

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

A comprehensive investigation on micro-structured surfaces for underwater drag reduction

2020 ◽  
Vol 218 ◽  
pp. 107902
Author(s):  
Tao Wu ◽  
Wei Chen ◽  
Aiguo Zhao ◽  
Peng He ◽  
Hong Chen
Keyword(s):  
Drag Reduction ◽  
Comprehensive Investigation ◽  
Structured Surfaces

Investigation on an integrated approach to design and micro fly-cutting of micro-structured riblet surfaces

2016 ◽  
Vol 231 (18) ◽  
pp. 3291-3300 ◽  
Author(s):  
Feifei Jiao ◽  
Samira Sayad Saravi ◽  
Kai Cheng
Keyword(s):  
Drag Reduction ◽  
Integrated Approach ◽  
Micro Milling ◽  
Control Technique ◽  
Machined Surface ◽  
Structured Surfaces ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Fly Cutting ◽  
Cutting Processes

Drag reduction in wall-bounded flows can be achieved by the passive flow control technique through the application of bio-inspired ribleted surfaces. In this paper, innovative design and manufacturing of serrate-semi-circular ribleted surfaces are presented with application to friction and drag reduction on engineering surfaces. Firstly, the design of the ribleted surfaces is described particularly focusing on the serrate-semi-circular shaped structures. Secondly, machining of ribleted surfaces by fly-cutting is investigated, covering the utilization of bespoke CVD diamond tools on a micro-milling machine and the corresponding micro fly-cutting processes. Metrology measurement results show good agreement achieved between the designed and machined surface features. Experiment conducted in wind tunnel shows the machined surface can produce 7% in drag reduction. Compared with conventional micro milling, the micro fly-cutting technique resulted from this research illustrates the unique advantage and industrial significance, particularly for manufacturing micro-structured surfaces in an industrial scale.

Assessment of drag reduction at slippery, topographically structured surfaces

2015 ◽  
Vol 19 (1) ◽  
pp. 199-207 ◽  
Author(s):  
Clarissa Schönecker ◽  
Steffen Hardt
Keyword(s):  
Drag Reduction ◽  
Structured Surfaces

scholarly journals Drag reduction via spanwise transversal traveling waves of smooth and structured surfaces

PAMM ◽  
2016 ◽  
Vol 16 (1) ◽  
pp. 641-642
Author(s):  
Pascal S. Meysonnat ◽  
Wolfgang Schröder
Keyword(s):  
Drag Reduction ◽  
Traveling Waves ◽  
Structured Surfaces

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’.

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