Kinetic Effects in Dynamic Wetting

Sprittles, James E.

doi:10.1103/physrevlett.118.114502

Cited by 44 publications

(37 citation statements)

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“…This range includes numerous physical systems characterised by scalesL = 0.1-7 µm at atmospheric pressure, and larger at reduced pressure, e.g. for recent applications in free surface flows (Sprittles 2017). Of initial interest are canonical flow problems, studied intensively for Stokes flow, including solid objects of various shapes in classical flows (shear, extensional, etc.)…”

Section: Discussionmentioning

confidence: 99%

Fundamental solutions to the regularised 13-moment equations: efficient computation of three-dimensional kinetic effects

et al. 2017

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Fundamental solutions (Green's functions) are derived for the regularised 13-moment system (R13) of rarefied gas dynamics, for small departures from equilibrium; these solutions show the presence of Knudsen layers, associated with exponential decay terms, that do not feature in the solution of lower-order systems (e.g. the Navier-Stokes-Fourier equations). Incorporation of these new fundamental solutions into a numerical framework based on the method of fundamental solutions (MFS) allows for efficient computation of three-dimensional gas microflows at remarkably low computational cost. The R13-MFS approach accurately recovers analytic solutions for low-speed flow around a stationary sphere and heat transfer from a hot sphere (for which a new analytic solution has been derived), capturing non-equilibrium flow phenomena missing from lower-order solutions. To demonstrate the potential of the new approach, the influence of kinetic effects on the hydrodynamic interaction between approaching solid microparticles is calculated. Finally, a programme of future work based on the initial steps taken in this article is outlined.

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Section: Discussionmentioning

confidence: 99%

Fundamental solutions to the regularised 13-moment equations: efficient computation of three-dimensional kinetic effects

et al. 2017

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“…Such a simplification reduces the problem to a two-dimensional geometry. While effective in describing the onset of the forced-wetting transition [23,24,[37][38][39][40][41], such analyses exclude the threedimensional structures that emerge at later stages. Our experiments show a pure two-dimensional analysis is no longer adequate in the steady state.…”

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confidence: 99%

Characteristic Interfacial Structure behind a Rapidly Moving Contact Line

Nagel

2019

Phys. Rev. Lett.

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In forced wetting, a rapidly moving surface drags with it a thin layer of trailing fluid as it is plunged into a second fluid bath. Using high-speed interferometry, we find characteristic structure in the thickness of this layer with multiple thin flat triangular structures separated by much thicker regions. These features, depending on liquid viscosity and penetration velocity, are robust and occur in both wetting and de-wetting geometries. Their presence clearly shows the importance of motion in the transverse direction. We present a model using the assumption that the velocity profile is robust to thickness fluctuations that gives a good estimate of the thin gap thickness.We measured the dependence of the gap dimensions on the liquid viscosity, substrate width, and penetration arXiv:1807.11910v2 [cond-mat.soft]

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“…When a droplet lands on a substrate, a thin layer of air will be trapped in between [1][2][3][4][5][6][7][8][9][10][11][12], which significantly affects the dynamics of the droplet [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Basic fluid mechanics tells us that it is very difficult to push fluid out of a narrow gap [29].…”

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confidence: 99%

Mechanism of Contact between a Droplet and an Atomically Smooth Substrate

Liu

2017

Phys. Rev. X

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When a droplet gently lands on an atomically smooth substrate, it will most likely contact the underlying surface in about 0.1 s. However, theoretical estimation from fluid mechanics predicts a contact time of 10-100 s. What causes this large discrepancy, and how does nature speed up contact by 2 orders of magnitude? To probe this fundamental question, we prepare atomically smooth substrates by either coating a liquid film on glass or using a freshly cleaved mica surface, and visualize the droplet contact dynamics with 30-nm resolution. Interestingly, we discover two distinct speed-up approaches: (1) droplet skidding due to even minute perturbations breaks rotational symmetry and produces early contact at the thinnest gap location, and (2) for the unperturbed situation with rotational symmetry, a previously unnoticed boundary flow around only 0.1 mm=s expedites air drainage by over 1 order of magnitude. Together, these two mechanisms universally explain general contact phenomena on smooth substrates. The fundamental discoveries shed new light on contact and drainage research.

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Kinetic Effects in Dynamic Wetting

Cited by 44 publications

References 46 publications

Fundamental solutions to the regularised 13-moment equations: efficient computation of three-dimensional kinetic effects

Fundamental solutions to the regularised 13-moment equations: efficient computation of three-dimensional kinetic effects

Characteristic Interfacial Structure behind a Rapidly Moving Contact Line

Mechanism of Contact between a Droplet and an Atomically Smooth Substrate

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