Microbubble skin friction reduction on an axisymmetric body

Deutsch, Steven; Castano, John M.

doi:10.1063/1.865786

Cited by 48 publications

(18 citation statements)

References 11 publications

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“…Hence, for those etched surfaces, water molecules could not directly contact the surface of the fluoropolyurethane, and these surface characteristics could reduce the friction factor. As for continuously increasing the Reynolds number and flow rate, the non-shear air-water interface might become thinner and thinner [45,46]. However, the superhydrophilic drag reduction effect was even more obvious than the superhydrophobic.…”

Section: Microchannel Drag-reduction Analysismentioning

confidence: 99%

Fabrication of Zinc Substrate Encapsulated by Fluoropolyurethane and Its Drag-Reduction Enhancement by Chemical Etching

Cui

Zhu

et al. 2020

Coatings

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A fluoropolyurethane-encapsulated process was designed to rapidly fabricate low-flow resistance surfaces on the zinc substrate. For the further enhancement of the drag-reduction effect, Cu2+-assisted chemical etching was introduced during the fabrication process, and its surface morphology, wettability, and flow-resistance properties in a microchannel were also studied. It is indicated that the zinc substrate with a micro-nanoscale roughness obtained by Cu2+-assisted nitric acid etching was superhydrophilic. However, after the etched zinc substrate is encapsulated with fluoropolyurethane, the superhydrophobic wettability can be obtained with a contact angle of 154.8° ± 2.5° and a rolling angle of less than 10°. As this newly fabricated surface was placed into a non-standard design microchannel, it was found that with the increase of Reynolds number, the drag-reduction rate of the superhydrophobic surface remained basically unchanged at 4.0% compared with the original zinc substrate. Furthermore, the prepared superhydrophobic surfaces exhibited outstanding reliability in most liquids.

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Section: Microchannel Drag-reduction Analysismentioning

confidence: 99%

Fabrication of Zinc Substrate Encapsulated by Fluoropolyurethane and Its Drag-Reduction Enhancement by Chemical Etching

Cui

Zhu

et al. 2020

Coatings

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“…Their data showed that BDR improved with decreasing flow speed, increasing gas injection rates, and when buoyancy assisted in retaining the bubbles in the boundary layer. Deutsch & Castano (1986) studied BDR on an axisymmetric body that was 0.089 m in diameter and 0.62 m in total length for Re L < 10 7 and gas injection rates corresponding to 0 <ᾱ < 1. They showed that drag reduction improved with increasing Fr as the influence of buoyancy was reduced and the bubbles stayed closer to the surface of the body.…”

Section: Experimental Observation Of Bubble Drag Reduction With Gas Imentioning

confidence: 99%

Friction Drag Reduction of External Flows with Bubble and Gas Injection

Ceccio

2010

Annu. Rev. Fluid Mech.

466

248

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The lubrication of external liquid flow with a bubbly mixture or gas layer has been the goal of engineers for many years, and this article presents the underlying principles and recent advances of this technology. It reviews the use of partial and supercavities for drag reduction of axisymmetric objects moving within a liquid. Partial cavity flows can also be used to reduce the friction drag on the nominally two-dimensional portions of a horizontal surface, and the basic flow features of two-dimensional cavities are presented. Injection of gas can lead to the creation of a bubbly mixture near the flow surface that can significantly modify the flow within the turbulent boundary layer, and there have been significant advances in the understanding of the underlying physical process of drag reduction. Moreover, with sufficient gas flux, the bubbles flowing beneath a solid surface can coalesce to form a thin drag-reducing air layer. The current applications of these techniques to underwater vehicles and surface ships are discussed.

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“…This pioneering work was followed by several experimental investigations conducted in the former Soviet Union (9), (10) where they reported a significant drag reduction in water tunnel boundary layers by injection of air bubbles through porous plates. In the 1980s, through a series of systematic studies in water tunnels, the drag reduction on a flat plate due to micro-bubbles generated by porous plates (11) -(14) and on axisymmetric body by circumferential porous rings (15) - (17) , were observed with values up to 80%. More recently, several investigations of a flat plate tunnel boundary layer were carried out to study the effect of bubble size and bubble concentration on the reduction of skin friction (18) - (26) .…”

Section: Introductionmentioning

confidence: 99%

Drag Reduction Effects of Micro-Bubbles in Straight and Helical Pipes

Shatat

Yanase

Takami

et al. 2009

JFST

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Experimental investigations were conducted to study the effect of micro-bubbles injected into water flowing through straight and helical pipes with different curvature ( 0.025, 0.05 and 0.1). The micro-bubbles were produced using two hydrocyclone micro-bubble generators positioned face to face with opposite direction of swirl flow. The mean diameter of the micro-bubbles generated was about 60 μm, while the maximum diameter observed was 174 μm, with air fraction, which will be defined in Eq.(4), ranging from 0.21% to 0.44%. The effect of the Reynolds number on the drag reduction is also presented. The experimental results show that, the micro-bubble has an effect of drag reduction on both straight and helical pipes, though the drag reduction in a straight pipe is much higher than that in a helical pipe, because of the secondary flow in a helical pipe. It is found that the drag reduction increases with the decrease of curvature and the increase of air fraction. The maximum value of drag reduction ratio was 51% in case of a straight pipe, while that for a helical pipe was 16%.

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Microbubble skin friction reduction on an axisymmetric body

Cited by 48 publications

References 11 publications

Fabrication of Zinc Substrate Encapsulated by Fluoropolyurethane and Its Drag-Reduction Enhancement by Chemical Etching

Fabrication of Zinc Substrate Encapsulated by Fluoropolyurethane and Its Drag-Reduction Enhancement by Chemical Etching

Friction Drag Reduction of External Flows with Bubble and Gas Injection

Drag Reduction Effects of Micro-Bubbles in Straight and Helical Pipes

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