Early stage of nanodroplet impact on solid wall

Kobayashi, Kazumichi; Konno, K.; Yaguchi, Hisao; Fujii, Hiroyuki; Sanada, Toshiyuki; Watanabe, Masao

doi:10.1063/1.4942874

Cited by 28 publications

(11 citation statements)

References 20 publications

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“…MD studies, which changed wettability by varying a liquid-solid interaction parameter, have been conducted to compare behaviors of impacting droplet with experiments on several wettabilities [25,26] Owing to the intermolecular force between argon and platinum molecules, vapor argon molecules could adhere to the platinum wall and a thin argon film was formed on the wall before the impact of liquid droplet. This formation of the thin film occurred only the case at V 0 = 100 m/s because of the impact time of the droplet in this simulation.…”

Section: Calculation Modelmentioning

confidence: 99%

“…In this study, we used the double-cylinder control volumes [26] shown in Fig. 4 to calculate the density or temperature field under the assumption that the droplet impact had axial symmetry.…”

Section: Definition Of Leidenfrost Effectmentioning

confidence: 99%

“…Kobayashi et al [26] showed that there was little influence of the intermolecular force from the wall on the liquid molecules in the fourth or higher layer of the control volumes because of the balance between the cutoff radius and height of the layer. Hence, we defined the onset of the Leidenfrost effect as the case in which the droplet (liquid phase) levitates over the Layer 4 of the control volumes.…”

Section: Definition Of Leidenfrost Effectmentioning

confidence: 99%

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Influence of liquid–solid intermolecular force on levitation of impacting nanodroplet

et al. 2018

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When droplets impact on a heated wall, they can levitate owing to the vapor stream generated by the droplet evaporation. This phenomenon is called the Leidenfrost effect, and the vapor layer prevents heat transfer between the droplet and heated wall. In this study, we investigated the influence of the intermolecular force between liquid and solid molecules on the levitating phenomenon, which is caused by heat transfer, for nanodroplets. We used a molecular dynamics (MD) simulation to evaluate the detailed behavior of droplet levitation and investigated the temperature field of the impacting droplet. We found that the droplet levitation was likely to occur at lower temperature when the intermolecular force was stronger. In addition, when the intermolecular force was strong enough, the liquid molecules stayed on the heated wall and an adsorption layer was formed. This adsorption layer exceeded the critical temperature of the liquid molecules, and the existence of the adsorption layer significantly affected the onset of the droplet levitation. IntroductionThe impact of droplets on a heated wall can be seen in spray cooling for heated steel, electronic devices, and other settings and applications [1,2]. The utilized droplets have become smaller (tens of a micrometer) and faster (tens of m/s) with the recent progression of technology [3]. When a droplet impacts

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Section: Calculation Modelmentioning

confidence: 99%

Section: Definition Of Leidenfrost Effectmentioning

confidence: 99%

Section: Definition Of Leidenfrost Effectmentioning

confidence: 99%

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Influence of liquid–solid intermolecular force on levitation of impacting nanodroplet

et al. 2018

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“…However, it is challenging to conduct experimental research for such droplets. In contrast, molecular dynamics (MD) simulations provide an alternative way of investigating various dynamic behaviors of nanoscale droplets, such as spreading, splashing, rebound, and coalescence . By means of MD simulations, some useful attempts − have been devoted to developing models of the maximum spreading factor for nanoscale impacting droplets.…”

Section: Introductionmentioning

confidence: 99%

Universal Model for the Maximum Spreading Factor of Impacting Nanodroplets: From Hydrophilic to Hydrophobic Surfaces

et al. 2020

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Using molecular dynamics (MD) simulations, we investigate impact behaviors of water nanodroplets on hydrophilic to hydrophobic surfaces with static contact angles ranging from 21 to 148°in a wide Weber number range of 15−90, aiming to understand how the surface wettability influences the maximum spreading factor of nanodroplets. We show that the existing macroscale and nanoscale models cannot capture the influence of surface wettability on the maximum spreading factor. We demonstrate that the failure is attributed to the rough estimation of the spreading velocity during the spreading stage, which is assumed to be a constant value in these models. We show that the spreading velocity strongly depends on both the surface wettability and the Weber number. After scaling with the impact velocity, we obtain a universal function of the spreading velocity with respect to the static contact angle and the Weber number. We employ this function to modify the expression of viscous dissipation and develop a new model of the maximum spreading factor. We verify that the model is in excellent agreement with the MD simulations regardless of hydrophilic and hydrophobic surfaces, with the mean relative deviation ranging from 0.88 to 4.75%. We also provide evidence to support the fact that incorporating the influence of surface wettability by modifying viscous dissipation is more reasonable than by modifying surface energy for nanodroplet impact.

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“…At the end of this wetting phase, the droplet reaches equilibrium, i.e., the velocity of the contact line between the droplet and the surface becomes zero. These findings of Rioboo et al [21] and Schiaffino and Sonnin [20] have been used in several recent studies [25][26][27][28][29] investigating the droplet spreading phenomenon on a variety of surfaces. Figure 3a shows the schematic of the experimental setup used to perform the high-speed imaging studies on the droplets.…”

Section: Droplet Spreading Behaviorsmentioning

confidence: 98%

Droplet spreading characteristics observed during 3D printing of aligned fiber-reinforced soft composites

Picha¹,

Spackman²,

Samuel³

2016

Additive Manufacturing

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The 3D printing of fiber-reinforced soft composites (FrSCs) is a hybrid process that combines conventional inkjet-based 3D printing with the directed deposition of electrospun polymer fiber mats. This paper investigates the spreading characteristics of droplets when deposited on fibrous substrates, under conditions relevant to 3D printing of aligned FrSCs. Both single and multidroplet impingement studies are conducted on substrates with varying fiber number densities. High-speed imaging is used to study the characteristic time-scales and the spreading behavior of the droplets. The single droplet impingement studies on stationary substrates reveal that the presence of fibers promotes droplet spreading along the length the fibers. Occasional surface energy variations in the fiber mats in the form of voids and fiber bundles are also seen to affect the droplet shape and the characteristic spreading times. In the case of a moving substrate, the droplets are seen to spread the most during in-line printing, i.e., when the direction of the printing velocity coincides with the direction of fiber alignment. They spread the least during orthogonal printing, i.e., when the direction of the printing velocity is perpendicular to the direction of fiber alignment. The printing of straight lines shows an interesting edge retraction phenomenon that gets accentuated the most in the case of in-line printing. The findings of the high-speed imaging studies have been confirmed by 3D printing comparable artifacts using UV curable inks. These studies indicate that for a given fiber mat and UV curable ink combination, the choice of the in-line or orthogonal printing strategy has implications for the overall printing time, fiber content, edge resolution and surface quality of the 3D printed FrSC part.

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Early stage of nanodroplet impact on solid wall

Cited by 28 publications

References 20 publications

Influence of liquid–solid intermolecular force on levitation of impacting nanodroplet

Influence of liquid–solid intermolecular force on levitation of impacting nanodroplet

Universal Model for the Maximum Spreading Factor of Impacting Nanodroplets: From Hydrophilic to Hydrophobic Surfaces

Droplet spreading characteristics observed during 3D printing of aligned fiber-reinforced soft composites

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