Contact Time of a Bouncing Nanodroplet

Xie, Fang-Fang; Lv, Shu-Hang; Yang, Yan‐Ru; Wang, Xiao‐Dong

doi:10.1021/acs.jpclett.0c00788

Cited by 59 publications

(31 citation statements)

References 43 publications

(93 reference statements)

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“…As shown in figure 3(a), the droplet bounces off the surface at 60 ps for D 0 = 8 nm, 85 ps for D 0 = 10 nm and 135 ps for D 0 = 14 nm. Xie et al (2020) investigated the contact time of nanodroplets on superhydrophobic surfaces. These authors noted that, unlike millimetre-sized droplets, the effects of liquid viscosity cannot be ignored for nanodroplets in a high-Weber-number range even for low-viscosity fluids; therefore, they developed further a new scaling law of contact time, expressed as τ c ∼ τ c,h = (D 0 /V 0 )We 2/3 Re −1/3 , where τ c,h is a characteristic time scale of bouncing nanodroplets at high velocities.…”

Section: Resultsmentioning

confidence: 99%

“…Because of the increased viscosity effect, the methods based on the energy balance between kinetic energy and surface energy (Laan et al 2014) or those based on the force balance between inertial force and capillary force (Clanet et al 2004) fail to derive the scaling law of β max for impacting nanodroplets at high velocities. Inspired by the scaling law of contact time by Xie et al (2020), the data of β/β max for the three nanodroplets in the high-Weber-number range are replotted in figure 3(b) using t/τ c,h as the abscissa. Interestingly, all the data collapse onto a single curve, indicating that there is a universal function β/β max = f (t/τ c,h ).…”

Section: Resultsmentioning

confidence: 99%

“…The lattice constant for fcc platinum is 3.92 Å (Padilla Espinosa, Jacobs & Martini 2021). The bottom three-layer atoms in the platinum substrate are fixed at their initial positions by virtual springs to prevent the substrate deformation during impact (Li et al 2015(Li et al , 2017Xie et al 2018Xie et al , 2020Wang et al 2019Wang et al , 2020a. Here, the value of the spring constant is chosen as 80 N m −1 , which is sufficient to avoid the substrate deformation based on our tests.…”

Section: Simulation Methodsmentioning

confidence: 99%

“…Thus, low-viscosity fluids at the nanoscale would naturally become 'high-viscosity' fluids. Xie et al (2020) investigated the contact time for water and argon nanodroplets impacting superhydrophobic surfaces and found that the contact time scales as…”

Section: Introductionmentioning

confidence: 99%

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Scaling laws of the maximum spreading factor for impact of nanodroplets on solid surfaces

Wang

Zhang

et al. 2022

J. Fluid Mech.

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This study investigates the dynamics of low-viscosity nanodroplets impacting surfaces with static contact angles from θ = 73° to 180° via molecular dynamics (MD) simulations. Two typical morphologies of impacting nanodroplets are observed at the maximum spreading state, a Hertz-ball-like in a low-Weber-number range and a thin-film-like in a high-Weber-number range. Only inertial and capillary forces dominate the impact for the former, whereas viscous force also becomes dominant for the latter. Regardless of morphologies at the maximum spreading state, the ratio of spreading time to contact time always remains constant on an ideal superhydrophobic surface with θ = 180°. With the help of different kinematic approximations of the spreading time and scaling laws of the contact time, scaling laws of the maximum spreading factor ${\beta _{max}}\sim W{e^{1/5}}$ in the low-Weber-number range (capillary regime) and ${\beta _{max}}\sim W{e^{2/3}}R{e^{ - 1/3}}$ (or ${\beta _{max}}\sim W{e^{1/2}}O{h^{1/3}}$ ) in the high-Weber-number range (cross-over regime) are obtained. Here, We, Re, and Oh are the Weber number, Reynolds number, and Ohnesorge number, respectively. Although the scaling laws are proposed only for the ideal superhydrophobic surface, they are tested valid for θ over 73° owing to the ignorable zero-velocity spreading effect. Furthermore, combining the two scaling laws leads to an impact number, $W{e^{3/10}}O{h^{1/3}} = 2.1$ . This impact number can be used to determine whether viscous force is ignorable for impacting nanodroplets, thereby distinguishing the capillary regime from the cross-over regime.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Simulation Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Scaling laws of the maximum spreading factor for impact of nanodroplets on solid surfaces

Wang

Zhang

et al. 2022

J. Fluid Mech.

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“…Molecular dynamics (MD) simulations provide a powerful tool to probe the dynamical behaviors of nanodroplets on an atomic scale. The mechanisms of spreading, break-up, bouncing, and other behaviors of nanodroplets are discussed via MD [15][16][17][18][19]. Chen et al simulated polymer nanodroplets impinging on a solid surface and found that the viscous dissipation of water nanodroplets stemmed from the velocity gradients in both the impinging and spreading directions [20].…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation on Behaviors of Water Nanodroplets Impinging on Moving Surfaces

2022

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Droplets impinging on solid surfaces is a common phenomenon. However, the motion of surfaces remarkably influences the dynamical behaviors of droplets, and related research is scarce. Dynamical behaviors of water nanodroplets impinging on translation and vibrating solid copper surfaces were investigated via molecular dynamics (MD) simulation. The dynamical characteristics of water nanodroplets with various Weber numbers were studied at four translation velocities, four vibration amplitudes, and five vibration periods of the surface. The results show that when water nanodroplets impinge on translation surfaces, water molecules not only move along the surfaces but also rotate around the centroid of the water nanodroplet at the relative sliding stage. Water nanodroplets spread twice in the direction perpendicular to the relative sliding under a higher surface translation velocity. Additionally, a formula for water nanodroplets velocity in the translation direction was developed. Water nanodroplets with a larger Weber number experience a heavier friction force. For cases wherein water nanodroplets impinge on vibration surfaces, the increase in amplitudes impedes the spread of water nanodroplets, while the vibration periods promote it. Moreover, the short-period vibration makes water nanodroplets bounce off the surface.

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Understanding and Utilizing Droplet Impact on Superhydrophobic Surfaces: Phenomena, Mechanisms, Regulations, Applications, and Beyond

Hu,

Chu,

Shan

et al. 2023

Advanced Materials

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Droplet impact is a ubiquitous liquid behavior that closely tied to human life and production, making indispensable impacts on the big world. Nature‐inspired superhydrophobic surfaces provide a powerful platform for regulating droplet impact dynamics. The collision between classic phenomena of droplet impact and the advanced manufacture of superhydrophobic surfaces is lighting up the future. Accurately understanding, predicting, and tailoring droplet dynamic behaviors on superhydrophobic surfaces are progressive steps to integrate the droplet impact into versatile applications and further improve the efficiency. In this review, the progress on phenomena, mechanisms, regulations, and applications of droplet impact on superhydrophobic surfaces, bridging the gap between droplet impact, superhydrophobic surfaces, and engineering applications are comprehensively summarized. It is highlighted that droplet contact and rebound are two focal points, and their fundamentals and dynamic regulations on elaborately designed superhydrophobic surfaces are discussed in detail. For the first time, diverse applications are classified into four categories according to the requirements for droplet contact and rebound. The remaining challenges are also pointed out and future directions to trigger subsequent research on droplet impact from both scientific and applied perspectives are outlined. The review is expected to provide a general framework for understanding and utilizing droplet impact.

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Contact Time of a Bouncing Nanodroplet

Cited by 59 publications

References 43 publications

Scaling laws of the maximum spreading factor for impact of nanodroplets on solid surfaces

Scaling laws of the maximum spreading factor for impact of nanodroplets on solid surfaces

Molecular Dynamics Simulation on Behaviors of Water Nanodroplets Impinging on Moving Surfaces

Understanding and Utilizing Droplet Impact on Superhydrophobic Surfaces: Phenomena, Mechanisms, Regulations, Applications, and Beyond

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