How surface roughness promotes or suppresses drop splash

Zhang, Haixiang; Zhang, Xiwen; Yi, Xian; Du, Yanxia; He, Feng; Niu, Fenglei; Hao, Pengfei

doi:10.1063/5.0079494

Cited by 19 publications

(9 citation statements)

References 58 publications

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“…In previous studies of droplet impact, most research scholars have focused on the effect of 2D surface roughness parameters on droplet splash. The 2D profile arithmetic deviation R a is the more commonly used of the many 2D surface roughness parameters and is defined as follows: [24] R a =…”

Section: Resultsmentioning

confidence: 99%

Suppressed Droplet Splashing on Positively Skewed Surfaces for High‐Efficiency Evaporation Cooling

Wang,

Liu,

et al. 2024

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Two types of functional surfaces with the same roughness but completely different surface topographies are prepared, namely positively skewed surfaces filled with micropillar arrays (Sa ≈4.4 µm, Ssk >0) and negatively skewed surfaces filled with microcavity arrays (Sa ≈4.4 µm, Ssk <0), demonstrating promoting droplet splashing. Remarkably, the critical Weber number for generating satellite droplets on the negatively skewed surfaces is significantly lower than that on the positively skewed surfaces, indicating that the negatively skewed surface with microcavity arrays is more likely to promote droplet splashing. It is mainly attributed to the fact that air on the negatively skewed surface can make the liquid film take on a Cassie‐Baxter state on the surface so that the stabilizing capillary force of the liquid film exceeds the destabilizing stress of the air film. Moreover, the surface topography promoting droplet spreading and the mechanical properties of three‐phase moving contact lines are analyzed from the perspective of microscopic interface mechanics. Finally, it is demonstrated the designed positively skewed surfaces can be employed for large‐area heat dissipation by means of high‐efficiency evaporation.

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Section: Resultsmentioning

confidence: 99%

Suppressed Droplet Splashing on Positively Skewed Surfaces for High‐Efficiency Evaporation Cooling

Wang,

Liu,

et al. 2024

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“…Based on the above discussion, this research adopts the splash threshold of Quintero et al, expands the model of García-Geijo et al (hereafter referred to as the G-model) to predict the spreading and splashing process of droplets on an inclined superhydrophobic surface, and provides a theoretical explanation for the experimental phenomenon that an upward liquid sheet on an inclined superhydrophobic wall can splash more easily and for the differences between cases of smooth and superhydrophobic substrates. Additionally, the gradual evolution between splashing and spreading has not been described in earlier works ,,, but does exist in practice. In this research, we attempt to predict the transition interval between spreading and splashing for the first time to more closely describe the actual situation.…”

Section: Introductionmentioning

confidence: 93%

Upward Splashing of a Droplet Impacting an Inclined Superhydrophobic Surface

Zhang,

Yao

2024

Langmuir

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It has long been held that when a droplet impacts obliquely onto a smooth dry surface at normal ambient temperature and pressure, upward splashing can be more easily suppressed than downward splashing. However, in this research, we experimentally find that for a superhydrophobic surface, increasing the wall inclination beforehand suppresses downward splashing and subsequently suppresses upward splashing. The spreading theory for an inclined surface is modified to predict the spreading process on an inclined superhydrophobic wall. Due to the existence of an asymmetric boundary layer between the upward and downward sheet on an inclined wall, the thickness and growth rate of the upward rim are smaller than those of the downward rim; for this reason, the upward side of the spreading sheet splashes more easily on a superhydrophobic wall, considering the theory of a droplet splashing on a flat surface. However, because the upward rim velocity is smaller than the downward rim velocity, the downward lamella splashes more easily than the upward lamella on a smooth surface. We attempt to theoretically describe the interval of the stochastic flow mode (spreading/splashing) that exists in practice for the first time. We also give the phase diagram containing three flow patterns, namely, two-side spreading, upward-only splashing, and two-side splashing, in the parameter space of the Weber number We and the wall inclination angle χ. The theory agrees well with the experimental results.

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“…Most often, the relationships between the occurrence of splashing and each of these parameters are not simply monotonic, but rather there is an interplay between two or more of them. Sometimes, a given parameter can either promote or suppress splashing depending on other parameters [29][30][31]. Furthermore, splashing can happen in different ways, including as a prompt splash, corona splash, receding breakup, and magic carpet breakup [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Prediction of the morphological evolution of a splashing drop using an encoder–decoder

Yee¹,

Igarashi²,

Miyatake³

et al. 2023

Mach. Learn.: Sci. Technol.

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The impact of a drop on a solid surface is an important phenomenon that has various implications and applications. However, the multiphase nature of this phenomenon causes complications in the prediction of its morphological evolution, especially when the drop splashes. While most machine-learning-based drop-impact studies have centred around physical parameters, this study used a computer-vision strategy by training an encoder-decoder to predict the drop morphologies using image data. Herein, we show that this trained encoder-decoder is able to successfully generate videos that show the morphologies of splashing and non-splashing drops. Remarkably, in each frame of these generated videos, the spreading diameter of the drop was found to be in good agreement with that of the actual videos. Moreover, there was also a high accuracy in splashing/non-splashing prediction. These findings demonstrate the ability of the trained encoder-decoder to generate videos that can accurately represent the drop morphologies. This approach provides a faster and cheaper alternative to experimental and numerical studies.

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How surface roughness promotes or suppresses drop splash

Cited by 19 publications

References 58 publications

Suppressed Droplet Splashing on Positively Skewed Surfaces for High‐Efficiency Evaporation Cooling

Suppressed Droplet Splashing on Positively Skewed Surfaces for High‐Efficiency Evaporation Cooling

Upward Splashing of a Droplet Impacting an Inclined Superhydrophobic Surface

Prediction of the morphological evolution of a splashing drop using an encoder–decoder

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