Modeling of the deformation of a liquid droplet impinging upon a flat surface

Fukai, Jun; Zhao, Zhiguo; Poulikakos, Dimos; Megaridis, Constantine M.; Miyatake, Osamu

doi:10.1063/1.858724

Cited by 274 publications

(170 citation statements)

References 28 publications

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“…This was confirmed later experimentally [23,25], and it was found that β grows with time according to a power law, with an exponent between 0.45 and 0.57 [25]. Since then, several studies on drop impact have focused on determining the maximum spreading factor β max , which is defined as the ratio of maximum spreading diameter d max to initial drop diameter d 0 [26,27]. For viscous liquids and superhydrophobic or partially wettable surfaces, Clanet et al [26] proposed that β max depended on a balance between inertia and surface tension.…”

Section: Introductionmentioning

confidence: 59%

Comparison of spontaneous wetting and drop impact dynamics of aqueous surfactant solutions on hydrophobic polypropylene surfaces: scaling of the contact radius

2014

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In this paper, we comparatively investigated the spontaneous wetting and the impact dynamics of surfactantladen drops on hydrophobic polypropylene surfaces. We used the organic anionic surfactant sodium dodecyl sulfate (SDS) and two silicone-based nonionic surfactants, one of which was a so-called superspreader. The wetting dynamics during spontaneous spreading could be divided into an early inertiadominated stage and a later viscosity-dominated stage. Both could be described by power laws with different exponents. Further, wetting dynamics during the faster inertial stage was independent of surfactant properties, while surfactants played a role in the slower viscous stage. During drop impact, regardless of the impact speed the early wetting stage was controlled by inertial and capillary forces only. But, different from spontaneous spreading, surfactants influenced the wetting dynamics of this early stage. After the drops reached the maximum spreading radius r max they started recoiling and reducing again their contact radius. We observed, however, that despite reducing the static surface tension of the water drops, not all surfactants promoted them to spread out to a larger radius than the pure water drops during the early impact stage. We thus introduced a new time scale, τ ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi ρr 3 max =γ p , that uses the maximum spreading radius of the drops upon impact and that allows rescaling the durations of the inertial wetting stages to a universal master curve. Finally, we observed that only those drops containing superspreader restarted wetting the surface after recoiling, but the dynamics is not yet completely clear.

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Section: Introductionmentioning

confidence: 59%

Comparison of spontaneous wetting and drop impact dynamics of aqueous surfactant solutions on hydrophobic polypropylene surfaces: scaling of the contact radius

2014

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“…For a normal solid, a similar situation is observed (cf. figure 3 of Fukai et al 1993), although a thin layer of liquid remains at the centre. Whether dry-out is achieved or not can be an important practical piece of information, and we discuss it in § 3.…”

Section: Introductionmentioning

confidence: 99%

“…The entire drop lifts off, in contrast to the case of a normal (non-superhydrophobic) surface, for which a portion of the splatted drop remains on the surface (cf. figure 4 of Fukai et al 1993;Pasandideh-Fard et al 1996;Bussmann, Mostaghimi & Chandra 1999).…”

Section: Introductionmentioning

confidence: 99%

Pyramidal and toroidal water drops after impact on a solid surface

et al. 2003

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Superhydrophobic surfaces generate very high contact angles as a result of their microstructure. The impact of a water drop on such a surface shows unusual features, such as total rebound at low impact speed. We report experimental and numerical investigations of the impact of approximately spherical water drops. The axisymmetric free surface problem, governed by the Navier-Stokes equations, is solved numerically with a front-tracking marker-chain method on a square grid. Experimental observations at moderate velocities and capillary wavelength much less than the initial drop radius show that the drop evolves to a staircase pyramid and eventually to a torus. Our numerical simulations reproduce this effect. The maximal radius obtained in numerical simulations precisely matches the experimental value. However, the large velocity limit has not been reached experimentally or numerically. We discuss several complications that arise at large velocity: swirling motions observed in the cross-section of the toroidal drop and the appearance of a thin film in the centre of the toroidal drop. The numerical results predict the dry-out of this film for sufficiently high Reynolds and Weber numbers. When the drop rebounds, it has a top-heavy shape. In this final stage, the kinetic energy is a small fraction of its initial value.

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“…Droplet dynamics at impact will be fundamentally different (Fukai et al, 1993;Pasandideh-Fard et al, 1995).…”

Section: Heat Transfer Phenomenamentioning

confidence: 99%

Investigation of Enhanced Surface Spray Cooling

Silk

Kim

Kiger

2004

Heat Transfer, Volume 2

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Phase change technology is a science that is continually finding new applications, from passive refrigeration cycles to semiconductor cooling. The primary heat transfer techniques associated with phase change heat transfer are pool boiling, flow boiling, and spray cooling. Of these techniques, spray cooling is the least studied and the most recent to receive attention in the scientific community. Spray cooling is capable of removing large amounts of heat between the cooled surface and the liquid, with reported heat flux capabilities of up to 1000 W/cm 2 for water. Many previous studies have emphasized heat flux as a function of spray parameters and test conditions.Enhanced spray cooling investigations to date have been limited to surface roughness studies. These studies concluded that surface tolerance (i.e. variations in machined surface finish) had an impact upon heat flux when using pressure atomized sprays.Analogous pool boiling studies with enhanced surfaces have shown heat flux enhancement. A spray cooling study using enhanced surfaces beyond the surface roughness range may display heat flux enhancement as well.In the present study, a group of extended and embedded surfaces (straight fins, cubic pin fins, pyramids, dimples and porous tunnels) have been investigated to determine the effects of enhanced surface structure on heat flux. The surface enhancements were machined on the top surface of copper heater blocks with a crosssectional area of 2.0 cm 2 . Measurements were also obtained on a flat surface for baseline comparison purposes. Thermal performance data was obtained under saturated (pure fluid at 101 kPa), nominally degassed (chamber pressure of 41.4 kPa) and gassy conditions (chamber with N 2 gas at 101 kPa). The study shows that both extended and embedded structures (beyond the surface roughness range) promote heat flux enhancement for both degassed and gassy spray cooling conditions. The study also shows that straight fins provide the best utilization of surface area added for heat transfer. An Energy conservation based CHF correlation for flat surface spray cooling was also developed. CHF predictions were compared against published and non-published studies by several researchers. Results for the correlations performanceshow an average mean error of ±17.6% with an accuracy of ±30% for 88% of the data set compared against.

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Modeling of the deformation of a liquid droplet impinging upon a flat surface

Cited by 274 publications

References 28 publications

Comparison of spontaneous wetting and drop impact dynamics of aqueous surfactant solutions on hydrophobic polypropylene surfaces: scaling of the contact radius

Comparison of spontaneous wetting and drop impact dynamics of aqueous surfactant solutions on hydrophobic polypropylene surfaces: scaling of the contact radius

Pyramidal and toroidal water drops after impact on a solid surface

Investigation of Enhanced Surface Spray Cooling

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