Slippage of Water over Nonwettable Surfaces

Schnell, E.

doi:10.1063/1.1722220

Cited by 159 publications

(113 citation statements)

References 3 publications

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“…The conclusions have been confirmed by Molecular Dynamics simulations [135] and are consistent with studies of flow in capillaries with diameters of tens of nanometers [3,91]. In this context, the large number of recent published experiments reporting some form of (apparent) slip with λ ∼ 1 nm−1 µm in the flow of Newtonian liquids is surprising [9,16,17,18,29,30,32,33,38,39,40,67,87,88,68,108,116,125,126,150,162,163,178,192,193,194,195], and has allowed to re-discover a few early [29] Poly(carbonate)+PVP SDS solutions studies reporting some degree of slip [21,34,46,141,160]. In part, this chapter is an attempt to describe and interpret these more recent experimental results.…”

Section: Newtonian Liquids: No-slip? Slip?supporting

confidence: 79%

Microfluidics: The No-Slip Boundary Condition

Lauga

Brenner

Stone

2007

Springer Handbook of Experimental Fluid Mechanics

585

674

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The no-slip boundary condition at a solid-liquid interface is at the center of our understanding of fluid mechanics. However, this condition is an assumption that cannot be derived from first principles and could, in theory, be violated. In this chapter, we present a review of recent experimental, numerical and theoretical investigations on the subject. The physical picture that emerges is that of a complex behavior at a liquid/solid interface, involving an interplay of many physico-chemical parameters, including wetting, shear rate, pressure, surface charge, surface roughness, impurities and dissolved gas.

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Section: Newtonian Liquids: No-slip? Slip?supporting

confidence: 79%

Microfluidics: The No-Slip Boundary Condition

Lauga

Brenner

Stone

2007

Springer Handbook of Experimental Fluid Mechanics

585

674

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“…The physical parameters (i.e., slip length, surface tension, contact angle, and density) used in the simulation are listed in Table 2. a The range of slip length, which is the interactions between fluids and solid surfaces, is based on literature data (Schnell, 1956;Churaev et al, 1984;Watanabe et al, 1999;Baudry et al, 2001;Craig et al, 2001;Tretheway and Meinhart, 2002;Cheng and Giordano, 2002;Jin et al, 2004;Joseph and Tabeling, 2005;Neto et al, 2005;Choi and Kim, 2006;Joly et al, 2006;Zhu et al, 2012;Li et al, 2014). b The lower limits of the surface tension of toluene-derived SOM were determined as 28 mN m −1 , the surface tension of liquid toluene at 293 K (Adamson and Gast, 1997).…”

Section: Poke-flow Technique In Conjunction With Fluid Simulationsmentioning

confidence: 99%

Relative humidity-dependent viscosity of secondary organic material from toluene photo-oxidation and possible implications for organic particulate matter over megacities

et al. 2016

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Abstract. To improve predictions of air quality, visibility, and climate change, knowledge of the viscosities and diffusion rates within organic particulate matter consisting of secondary organic material (SOM) is required. Most qualitative and quantitative measurements of viscosity and diffusion rates within organic particulate matter have focused on SOM particles generated from biogenic volatile organic compounds (VOCs) such as α-pinene and isoprene. In this study, we quantify the relative humidity (RH)-dependent viscosities at 295 ± 1 K of SOM produced by photo-oxidation of toluene, an anthropogenic VOC. The viscosities of toluene-derived SOM were 2 × 10 −1 to ∼ 6 × 10 6 Pa s from 30 to 90 % RH, and greater than ∼ 2 × 10 8 Pa s (similar to or greater than the viscosity of tar pitch) for RH ≤ 17 %. These viscosities correspond to Stokes-Einstein-equivalent diffusion coefficients for large organic molecules of ∼ 2 × 10 −15 cm 2 s −1 for 30 % RH, and lower than ∼ 3 × 10 −17 cm 2 s −1 for RH ≤ 17 %. Based on these estimated diffusion coefficients, the mixing time of large organic molecules within 200 nm toluene-derived SOM particles is 0.1-5 h for 30 % RH, and higher than ∼ 100 h for RH ≤ 17 %. As a starting point for understanding the mixing times of large organic molecules in organic particulate matter over cities, we applied the mixing times determined for toluene-derived SOM particles to the world's top 15 most populous megacities. If the organic particulate matter in these megacities is similar to the toluene-derived SOM in this study, in Istanbul, Tokyo, Shanghai, and São Paulo, mixing times in organic particulate matter during certain periods of the year may be very short, and the particles may be wellmixed. On the other hand, the mixing times of large organic molecules in organic particulate matter in Beijing, Mexico City, Cairo, and Karachi may be long and the particles may not be well-mixed in the afternoon (15:00-17:00 LT) during certain times of the year.

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“…A number of new studies have confirmed the existence of a liquid slip over certain solid surfaces, as summarized in recent reviews. [5][6][7] Although a few studies 8,9 have reported a slip over hydrophilic surfaces, many theoretical, 10,11 experimental, [12][13][14][15][16][17][18][19][20][21][22][23] and numerical 24 studies have reported that hydrophobic surfaces allow a noticeable slip ranging from nanometers to a micron in "slip length" ͑the linearly extrapolated distance into a solid surface at which a no-slip condition would hold true͒. Several reasons have been proposed for the slip over hydrophobic surfaces, including a molecular slip, 10 a decrease in the viscosity of the boundary layer, 11 the small dipole moment of a polar liquid, 23 and a gas gap or nanobubbles at the liquid-surface interface.…”

Section: Introductionmentioning

confidence: 99%

Effective slip and friction reduction in nanograted superhydrophobic microchannels

Choi¹,

Ulmanella²,

Kim³

et al. 2006

Physics of Fluids

410

266

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Enabled by a technology to fabricate well-defined nanogrates over a large area ͑2 ϫ 2 cm 2 ͒, we report the effect of such a surface, in both hydrophilic and hydrophobic conditions, on liquid slip and the corresponding friction reduction in microchannels. The grates are designed to be dense ͑ϳ230 nm pitch͒ but deep ͑ϳ500 nm͒ in order to sustain a large amount of air in the troughs when the grates are hydrophobic, even under pressurized liquid flow conditions ͑e.g., more than 1 bar͒. A noticeable slip ͑i.e., slip length of 100-200 nm, corresponding to 20%-30% reduction of pressure drop in a ϳ3 m high channel͒ is observed for water flowing parallel over the hydrophobic nanogrates; this is believed to be an "effective" slip generated by the nanostrips of air in the grate troughs under the liquid. The effective slip is clearer and larger in flows parallel to the nanograting patterns than in transverse, suggesting that the nanograted superhydrophobic surfaces would not only reduce friction in liquid flows under pressure but also enable directional control of the slip. This paper is the first to use nanoscale grating patterns and to measure their effect on liquid flows in microchannels.

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Slippage of Water over Nonwettable Surfaces

Cited by 159 publications

References 3 publications

Microfluidics: The No-Slip Boundary Condition

Microfluidics: The No-Slip Boundary Condition

Relative humidity-dependent viscosity of secondary organic material from toluene photo-oxidation and possible implications for organic particulate matter over megacities

Effective slip and friction reduction in nanograted superhydrophobic microchannels

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