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Impact of surface roughness on diffusion of confined fluids
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10.1063/1.3651478
/content/aip/journal/jcp/135/15/10.1063/1.3651478
http://aip.metastore.ingenta.com/content/aip/journal/jcp/135/15/10.1063/1.3651478
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Schematics of the geometries of the confined fluid system, as described in the text. (a) Featureless walls and (b) physically rough walls.

Image of FIG. 2.
FIG. 2.

Self diffusivity D versus total density ρ = N/(AH) for the hard-sphere fluid confined between smooth walls in slit-pore geometry.

Image of FIG. 3.
FIG. 3.

Self diffusivity D versus total density ρ for the hard-sphere fluid confined between thermal walls, for various wall separations H.

Image of FIG. 4.
FIG. 4.

Fraction of collisions in the system involving the wall surface f w for the hard-sphere fluid confined to a slit-pore geometry. Symbols have the same meaning as in Fig. 3.

Image of FIG. 5.
FIG. 5.

Ratio of the self-diffusivity between thermal walls D TW to its value when confined between smooth walls D SW at the same ρ and H versus (a) ρ and (b) H −1. Symbols in (a) are the same as those in Fig. 3. In (b), all data is for ρσ3 > 0.2, and dashed line is a fit to the form D TW/D SW = 1.0–1.44σ/H.

Image of FIG. 6.
FIG. 6.

Ratio of predicted to observed self diffusivity (see text) for the thermal wall system. Dotted blue and red dashed lines provide 5% and 25% error bounds, respectively. Symbols are the same as those in Fig. 3.

Image of FIG. 7.
FIG. 7.

Self diffusivity D RW versus density ρ for the hard-sphere fluid confined between rotational walls at (a) θ = π/2 and various wall separations H and (b) H/σ = 7 and various values of θ.

Image of FIG. 8.
FIG. 8.

Ratio of self diffusivity between rotational walls D RW to that between smooth walls D SW at the same ρ and H versus ρ at (a) θ = π/2 and various H and (b) H/σ = 7 and various θ, and versus (c) H −1 at various θ. Symbols in (a), and (b) and (c) are the same as those in Figs. 7(a) and 7(b), respectively. In (c), all data points are for ρσ3 > 0.2; lines are linear fits of the form D RW/D SW = 1 − C(H/σ)−1; the inset to (c) shows the value of C as a function of θ from linear fits in main panel of (c).

Image of FIG. 9.
FIG. 9.

Ratio of predicted to observed self diffusivity (discussed in text) versus the observed self diffusivity for the rotational wall system with the value of θ denoted in each figure. Dotted blue and red dashed lines provide 10% and 25% error bounds, respectively. Symbols have the same meaning as in Fig. 7(a).

Image of FIG. 10.
FIG. 10.

Self diffusivity in ((a) and (c)) smooth x and ((b) and (d)) rough y directions versus density for the hard-sphere fluid confined between physically rough walls (see Fig. 1) with λ/σ = 3.0 and ((a) and (b)) a w /σ = 1.0 and various H and ((c) and (d)) H/σ = 7.5 and various a w .

Image of FIG. 11.
FIG. 11.

Fraction of particle collisions that involve the wall f w for the hard-sphere fluid confined between physically rough walls versus density. (a) a w /σ = 1.0 at various H and (b) H/σ = 7.5 and various a w . Symbols have the same meaning as in Fig. 10.

Image of FIG. 12.
FIG. 12.

Ratio of self diffusivity in rough direction D y and smooth direction D x with λ/σ = 3.0 versus ((a) and (b)) ρ and (c) H −1 for the hard-sphere fluid confined between physically rough walls. Symbols in (a) and (c) are the same as in Fig. 10. In (c) all data points are for ρσ3 > 0.2 and lines are fits to the form D y /D x = 1 − C(H/σ)−1. Panel (d) displays the values of C versus a w at all the wavelengths studied.

Image of FIG. 13.
FIG. 13.

Ratio of predicted (see text) to observed value of D y plotted versus D y for the hard-sphere fluid confined between physically rough walls with λ/σ = 3.0 and ((a) and (b)) a w /σ = 1 and various H and ((c) and (d)) H/σ = 7.5 and various a w . Symbols in (a) and (b), and (c) and (d) correspond to those in Figs. 10(a) and 10(c), respectively. In (a) and (c) we use values of C obtained from the fits in Fig. 12(c), while in (b) and (d) we use C = 2.12a w /σ (see Fig. 12(d)). The dotted green and dashed red lines correspond to 10% and 25% error bounds, respectively.

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/content/aip/journal/jcp/135/15/10.1063/1.3651478
2011-10-17
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Impact of surface roughness on diffusion of confined fluids
http://aip.metastore.ingenta.com/content/aip/journal/jcp/135/15/10.1063/1.3651478
10.1063/1.3651478
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