Turbulent Drag Reduction Using Superhydrophobic Surfaces

Henoch, Charles; Krupenkin, Tom N.; Kolodner, Paul; Taylor, J. Ashley; Hodes, Marc; Lyons, Alan M.; Peguero, Charles; Breuer, Kenneth

doi:10.2514/6.2006-3192

Cited by 75 publications

(56 citation statements)

References 5 publications

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“…It appears that the drag of the present superhydrophobic coatings is smaller than that of the CSBC standard coating. This observation is similar to the results concluded by Henoch et al [6].…”

Section: -P5supporting

confidence: 83%

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An Experimental Study of Drag Reduction in a Pipe with Superhydrophobic Coating at Moderate Reynolds Numbers

Chen

Tsai

Kehr

et al. 2010

EPJ Web of Conferences

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Abstract. This paper experimentally investigates drag reduction, durability for operations and effects for preventing microorganism from adhering to the surface when the superhydrophobic coating is applied on a solid surface. The experiments are divided into two parts. In the first part, a pipe flow system was established to measure the drag and to test the durability of the micro-structure of superhydrophobic coating at average speeds varying from 1m/sec to 6m/sec. In the second part, we tested the effect for preventing microorganism from adhering to the surface by putting the coated steel plates into sea water. There are four different superhydrophobic coatings in the present study. The experimental results were compared to those applied by ship paint usually used at CSBC.

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Section: -P5supporting

confidence: 83%

“…It produces a well-organized pattern. Henoch et al [6] employed the deep reactive ion etching to form the nanograss structure. Their experimental data show that a drag reduction up to 50% was observed for laminar flow, compared to that by traditional laminar-boundary-layer flow prediction.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study of Drag Reduction in a Pipe with Superhydrophobic Coating at Moderate Reynolds Numbers

Chen

Tsai

Kehr

et al. 2010

EPJ Web of Conferences

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“…Turbulent flow experiments have reduced drag by up to 75% (13-16). However, a wide range of experiments have provided inconsistent results, with several studies reporting little or no drag reduction (16)(17)(18)(19)(20)(21)(22)(23)(24)(25).A key step toward solving this puzzle has come with the realization that surfactants could induce Marangoni stresses that impair drag reduction. This was first hypothesized to account for experiments that revealed little measurable slip (23, 24), in contradiction with available theoretical predictions based on the absence of surfactants (26)(27)(28)(29)(30)(31)(32)(33)(34).…”

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confidence: 99%

mentioning

confidence: 99%

Traces of surfactants can severely limit the drag reduction of superhydrophobic surfaces

Peaudecerf

Landel

Goldstein

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

162

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Superhydrophobic surfaces (SHSs) have the potential to achieve large drag reduction for internal and external flow applications. However, experiments have shown inconsistent results, with many studies reporting significantly reduced performance. Recently, it has been proposed that surfactants, ubiquitous in flow applications, could be responsible by creating adverse Marangoni stresses. However, testing this hypothesis is challenging. Careful experiments with purified water already show large interfacial stresses and, paradoxically, adding surfactants yields barely measurable drag increases. To test the surfactant hypothesis while controlling surfactant concentrations with precision higher than can be achieved experimentally, we perform simulations inclusive of surfactant kinetics. These reveal that surfactant-induced stresses are significant at extremely low concentrations, potentially yielding a no-slip boundary condition on the air-water interface (the "plastron") for surfactant concentrations below typical environmental values. These stresses decrease as the stream-wise distance between plastron stagnation points increases. We perform microchannel experiments with SHSs consisting of streamwise parallel gratings, which confirm this numerical prediction, while showing near-plastron velocities significantly slower than standard surfactant-free predictions. In addition, we introduce an unsteady test of surfactant effects. When we rapidly remove the driving pressure following a loading phase, a backflow develops at the plastron, which can only be explained by surfactant gradients formed in the loading phase. This demonstrates the significance of surfactants in deteriorating drag reduction and thus the importance of including surfactant stresses in SHS models. Our time-dependent protocol can assess the impact of surfactants in SHS testing and guide future mitigating designs.superhydrophobic surface | drag reduction | surfactant | Marangoni stress | plastron S uperhydrophobic surfaces (SHSs) combine hydrophobic surface chemistry and micro-or nanoscale patterning to retain a network of air pockets when exposed to a liquid (e.g., reviews in refs. 1-3). Because a large portion of the interface between the solid wall and the liquid is replaced by an air-liquid interface, which can be considered almost as a shear-free surface (known as a "plastron"), SHSs could be used to obtain significant drag reduction in fluid flow applications (4, 5). Microchannel tests have recorded drag reductions of over 20% (e.g., refs. 6-11) and rheometer tests reported slip lengths of up to 185 µm (12). Turbulent flow experiments have reduced drag by up to 75% (13-16). However, a wide range of experiments have provided inconsistent results, with several studies reporting little or no drag reduction (16)(17)(18)(19)(20)(21)(22)(23)(24)(25).A key step toward solving this puzzle has come with the realization that surfactants could induce Marangoni stresses that impair drag reduction. This was first hypothesized to account for experiments that rev...

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“…With only a few experimental data in the literature (Henoch et al 2006;Zhao et al 2007;Daniello et al 2009;Woolford et al 2009b;Peguero & Breuer 2009;Jung & Bhushan 2010) scattered by different Authors' final manuscript for: H. Park, G. Sun, and C.--J. Kim, "Superhydrophobic turbulent drag reduction as a function of surface grating parameters," Journal of Fluid Mechanics, Vol. 747, May 2014, pp.…”

Section: Introductionmentioning

confidence: 99%

Development of a Miniature Shear Sensor for Direct Comparison of Skin-Friction Drags

Sun

Park

Kim

2015

J. Microelectromech. Syst.

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Despite the confirmation of slip flows and successful drag reduction in small-scaled laminar flows, the full impact of superhydrophobic (SHPo) drag reduction remained questionable because of the sporadic and inconsistent experimental results in turbulent flows. Here we report a systematic set of bias-free reduction data obtained by measuring the skin-friction drags on a SHPo surface and a smooth surface at the same time and location in a turbulent boundary layer flow. Each monolithic sample consists of a SHPo surface and a smooth surface suspended by flexure springs, all carved out from a 2.7 × 2.7 mm 2 silicon chip by photolithographic microfabrication. The flow tests allow continuous monitoring of the plastron on the SHPo surfaces, so that the drag reduction data are genuine and consistent. A family ofSHPo samples with precise profiles reveals the effects of grating parameters on turbulent drag reduction, which was measured to be as much as ~ 75%.

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Turbulent Drag Reduction Using Superhydrophobic Surfaces

Cited by 75 publications

References 5 publications

An Experimental Study of Drag Reduction in a Pipe with Superhydrophobic Coating at Moderate Reynolds Numbers

An Experimental Study of Drag Reduction in a Pipe with Superhydrophobic Coating at Moderate Reynolds Numbers

Traces of surfactants can severely limit the drag reduction of superhydrophobic surfaces

Development of a Miniature Shear Sensor for Direct Comparison of Skin-Friction Drags

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