Experimental study on the reduction of skin frictional drag in pipe flow by using convex air bubbles

Kwon, Bong Hyun; Kim, Hyung Hoon; Jeon, Hae Jeong; Kim, Moon Chan; Lee, Inwon; Chun, Sejong; Go, Jeung Sang

doi:10.1007/s00348-014-1722-8

Cited by 14 publications

(10 citation statements)

References 27 publications

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“…Superhydrophobic tubes reported so far have been produced either by hydrophobic coating of a conventional tube 11 , 39 or by rolling of a superhydrophobic planar surface 6 , 40 , 41 . The coating approach has many challenges; 1: The coating procedure inside a tube can be challenging to optimize for high quality coatings, 2: A coating applied inside a tube is mostly not monolithic so its durability is limited, 3: The coatings are mostly fluorine-based with a possibility of contamination of the liquid and other environmental downsides.…”

Section: Introductionmentioning

confidence: 99%

Water and Blood Repellent Flexible Tubes

Hoshian

Kankuri

Ras

et al. 2017

Sci Rep

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A top-down scalable method to produce flexible water and blood repellent tubes is introduced. The method is based on replication of overhanging nanostructures from an aluminum tube template to polydimethylsiloxane (PDMS) via atomic layer deposition (ALD) assisted sacrificial etching. The nanostructured PDMS/titania tubes are superhydrophobic with water contact angles 163 ± 1° (advancing) and 157 ± 1° (receding) without any further coating. Droplets are able to slide through a 4 mm (inner diameter) tube with low sliding angles of less than 10° for a 35 µL droplet. The superhydrophobic tube shows up to 5,000 times increase in acceleration of a sliding droplet compared to a control tube depending on the inclination angle. Compared to a free falling droplet, the superhydrophobic tube reduced the acceleration by only 38.55%, as compared to a 99.99% reduction for a control tube. The superhydrophobic tubes are blood repellent. Blood droplets (35 µL) roll through the tubes at 15° sliding angles without leaving a bloodstain. The tube surface is resistant to adhesion of activated platelets unlike planar control titania and smooth PDMS surfaces.

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Section: Introductionmentioning

confidence: 99%

Water and Blood Repellent Flexible Tubes

Hoshian

Kankuri

Ras

et al. 2017

Sci Rep

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“…Bubbles can affect the state of fluid motion on a solid surface. The fluid motion in the surrounding air area satisfies the Navier-Stokes equation [28]. Figure 7(b) indicates the velocity field (where the red arrow is pointing) and flow field distribution (where the green arrow is pointing) of the falling superhydrophobic steel ball surface.…”

Section: Simulation Model and Theoretical Analysismentioning

confidence: 99%

Drag reduction of stable biomimetic superhydrophobic steel surface by acid etching under an oxygen-sufficient environment

Rong

Zhang

Mao

et al. 2020

Mater. Res. Express

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Superhydrophobic surfaces have shown utility applications in drag reduction field. A novel method based on simulation analysis and test experiments is proposed to fabricate a superhydrophobic surface with 3D flower-like micro and nano-structures on a steel ball under an O 2 rich environment. The superhydrophobic steel surface has water CA of 166±1.5°. The sliding angle is less than 2°. The experiment and the simulation of the superhydrophobic and the untreated steel ball fall under water are built to prove the validity of the method of reducing water resistance. The drag reduction ratio of the superhydrophobic steel ball is beyond 53% opposed to the untreated surface under water. A model simulation is built to simulate and analyze the solid-liquid interface drag reduction mechanism of superhydrophobic surface based on theoretical analysis. The result testifies the rationality of the drag reduction experiment.

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“…However, an additional energy supply is needed to operate the drag reduction system. The injection of tiny bubbles into the boundary layer has the effect of reducing the effective viscosity or Reynolds stress in the boundary layer, and many countries, including Japan, have been performing various bubble injection method experiments (Shen et al [2], Ceccio [3], Hara et al [4], Ojima et al [5], Kwon et al [6]). The gas drag reduction and gas cavity drag reduction researches were carried out by Elbing et al [7] and Mäkiharju et al [8].…”

Section: Introductionmentioning

confidence: 98%