Drop impact on superhydrophobic surface with protrusions

Jiang, Xiaofeng; Xu, Enle; Wu, Guoguang; Li, Huai Z.

doi:10.1016/j.ces.2019.115351

Cited by 29 publications

(10 citation statements)

References 33 publications

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“…Since then, various ridges have been designed to corroborate this method. Jiang et al 18 analyzed the contact time reduction of a droplet impacting a surface with three different protrusions (semicircle, triangle, and square). They found that the contact time tended to be the same on the three combined surfaces with We > 5, all of which could be reduced to 65% of the smooth surface.…”

Section: ■ Introductionmentioning

confidence: 99%

Impact Dynamics of a Droplet on Superhydrophobic Cylinders Structured with a Macro Ridge

et al. 2023

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Reducing the contact time of a droplet hitting a solid surface is crucial for many situations. In this work, the dynamic behavior of a low-viscosity droplet on a superhydrophobic surface, which consists of a cylindrical substrate and a macro ridge placed axially on the peak, was numerically investigated via the lattice Boltzmann method. The focus was given to the spreading and the detaching morphology of the droplet at the Weber number We = 0.84–37.8 and the cylinder-to-droplet radius ratio R* = 0.57–5.71. The ridge is found to redistribute the droplet mass and affect the impact outcomes, as well as the contact time. For each R*, a jug rebound, a stretched rebound straddling the ridge, and a split detachment occur sequentially with the increasing We. When R* does not exceed 1.71, the contact time decreases continuously with the increase in We. With R* being taken between 1.71 and 5.14, the contact time initially reduces with We and plateaus after We reaches 10.3. Once R* exceeds 5.14, the split droplets may present as a bestriding shape at We > 30.3 rather than the regular jug shape with a small We. The contact time would be decreased to a second plateau in this case. In most cases, the contact time can be shortened effectively for the droplet on a ridged cylinder compared with that of a smooth cylinder.

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Section: ■ Introductionmentioning

confidence: 99%

Impact Dynamics of a Droplet on Superhydrophobic Cylinders Structured with a Macro Ridge

et al. 2023

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“…For a droplet with low viscosity, the impact velocity and the cylinder size, represented by the Weber numbers ( We = 2ρ R 0 u 0 2 /σ, with u 0 referring to the initial velocity of the droplet) and the size ratio of the cylinder to the droplet ( R * = R cy / R 0 , where R cy refers to the cylinder radius), respectively, are two key factors affecting the dynamic behaviors of the droplet. For example, as We increases or R * decreases, the uneven distribution of the momentum becomes more pronounced, leading to a continuous reduction in contact time. ,, This feature is distinct from the constant value observed on smooth horizontal surfaces (τ c ≈ 2.6), or the discrete forms on flat substrates patterned with single-ridge (exhibiting a reduction rate of 25 and 50%) − or submillimeter-scale posts (showing a reduction rate up to 80%) . In an extreme case where a much higher We is applied or R * is much smaller, the droplet will directly break into smaller fragments, splash from the cylinder, or pass through the cylinder and fall off the surface, undergoing almost no retraction process. , When disregarding the aforementioned particular situations, considerable efforts have been made to correlate the contact time with the given conditions.…”

Section: Introductionmentioning

confidence: 92%

Contact Time of a Droplet Off-Centered Impacting a Superhydrophobic Cylinder

Zhang,

Chen,

Wang

et al. 2023

Langmuir

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Extensive research has shown that a superhydrophobic cylindrical substrate could lead to a noncircumferential symmetry of an impacting droplet, reducing the contact time accordingly. It is of practical significance in applications, such as anti-icing, anticorrosion, and antifogging. However, few accounts have adequately addressed the off-centered impact of the droplet, despite it being more common in practice. This work investigates the dynamic behavior of a droplet off-centered impacting a superhydrophobic cylinder via the lattice Boltzmann method. The effect of the off-centered distance is primarily discussed for droplets taking various Weber numbers and cylinder sizes. The results show that the imposition of an off-center distance can further disrupt the droplet symmetry during the impact. As the off-center distance increases, the droplet movement is gradually tilted toward the offset side until it tangentially passes the cylinder side, resulting in a direct dripping mode. The dynamic features, focusing mainly on maximum spreading in the axial direction and contact time, are specifically explored. A quantitative model of the maximum spreading factor is proposed based on the equivalent transformation from the off-center impact into oblique hitting, considering the full range of off-centered distance. A preliminary contact time model is established for droplet off-centered impacting superhydrophobic cylinders by substituting the maximum spreading and the effective velocity of the liquid moving. This work aims to make an original contribution to the fundamental knowledge of droplet impact and could be of value for related applications.

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“…In a typical experiment, from a predetermined height (thereby varying the impact velocity), a drop with a specific diameter is released from a syringe pump needle. The drop impact behavior is monitored by a high-speed camera ( Figure 26 ) [ 188 ]. Post impact dynamics are not only a function of density, impact velocity and viscosity but also a function of surface roughness, geometry, wettability, and mechanical strength [ 188 ].…”

Section: Characterization Of the Static And Dynamic Wetting Propertie...mentioning

confidence: 99%

“…The drop impact behavior is monitored by a high-speed camera ( Figure 26 ) [ 188 ]. Post impact dynamics are not only a function of density, impact velocity and viscosity but also a function of surface roughness, geometry, wettability, and mechanical strength [ 188 ]. Y. Shen, et al [ 189 ] achieved the minimum contact time on a complex textured SH surface.…”

Section: Characterization Of the Static And Dynamic Wetting Propertie...mentioning

confidence: 99%

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Advances in the Fabrication and Characterization of Superhydrophobic Surfaces Inspired by the Lotus Leaf

et al. 2022

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Nature has proven to be a valuable resource in inspiring the development of novel technologies. The field of biomimetics emerged centuries ago as scientists sought to understand the fundamental science behind the extraordinary properties of organisms in nature and applied the new science to mimic a desired property using various materials. Through evolution, living organisms have developed specialized surface coatings and chemistries with extraordinary properties such as the superhydrophobicity, which has been exploited to maintain structural integrity and for survival in harsh environments. The Lotus leaf is one of many examples which has inspired the fabrication of superhydrophobic surfaces. In this review, the fundamental science, supported by rigorous derivations from a thermodynamic perspective, is presented to explain the origin of superhydrophobicity. Based on theory, the interplay between surface morphology and chemistry is shown to influence surface wetting properties of materials. Various fabrication techniques to create superhydrophobic surfaces are also presented along with the corresponding advantages and/or disadvantages. Recent advances in the characterization techniques used to quantify the superhydrophobicity of surfaces is presented with respect to accuracy and sensitivity of the measurements. Challenges associated with the fabrication and characterization of superhydrophobic surfaces are also discussed.

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Drop impact on superhydrophobic surface with protrusions

Cited by 29 publications

References 33 publications

Impact Dynamics of a Droplet on Superhydrophobic Cylinders Structured with a Macro Ridge

Impact Dynamics of a Droplet on Superhydrophobic Cylinders Structured with a Macro Ridge

Contact Time of a Droplet Off-Centered Impacting a Superhydrophobic Cylinder

Advances in the Fabrication and Characterization of Superhydrophobic Surfaces Inspired by the Lotus Leaf

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