LANGMUIR
·
2024
·
IF 3.7
Weidong Fang,Zhi Tao,Haiwang Li,Yuqian Ma,Shuai Yin,Tiantong Xu,Teckneng Wong,Yi Huang
Emulsions have been applied in a number of industries such as pharmaceutics, cosmetics, and food, which are also of great scientific interest. Although aqueous emulsions are commonly used in our daily life, oil-in-oil (o/o) emulsions also play an irreplaceable role in view of their unique physics and complementary applications. In this paper, we investigate typical behaviors of organic droplets surrounded by organic medium (o/o emulsions) with different functional groups controlled by the AC electric field. Droplet behaviors can be catalogued into five types: namely, “no effect”, “movement”, “deformation”, “interface rupture”, and “disorder”. We identify the key dimensionless number Wee·Ca, combined with the channel geometry, for characterizing the typical behaviors in silicon oil/1,6-hexanediol diacrylate and mineral oil/1,6-hexanediol diacrylate emulsions. Unlike aqueous emulsion, the Maxwell–Wagner relaxation inhibits the electric effect and leads to an effective frequency, ranging from 0.5 to 3 kHz. The increasing viscosity of the droplet facilitates the escalation by promoting the shearing effect under the same flow conditions. Ethylene glycol droplets primarily show the efficient coalescence even at a low Wee·Ca, which is attributed to the attraction of free charges induced by the increasing conductivity. In 1,6-hexanediol diacrylate/silicon oil emulsion, the droplet tends to form a liquid film that expands into the entire channel due to the affinity of the droplet to the channel wall. A variety of elongated columns are observed to oscillate between the electrodes at high voltages. These findings can contribute to understanding the electrohydrodynamic physics in o/o emulsion and controlling droplet behaviors in a fast response, programmable, and high-throughput way. We expect that this droplet manipulation technology can be widely adopted in a broad range of chemical synthesis and biological and material science.
研究领域:
物理学
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化学工程
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
LANGMUIR
·
2023
·
IF 3.9
Hailong Liu,Nuo Zheng,Jiaqi Chen,Ding Yang,Junfeng Wang
The control of a droplet bouncing on a substrate is of great importance not only in academic research but also in practical applications. In this work, we focus on a particular type of non-Newtonian fluid known as shear-thinning fluid. The rebound behaviors of shear-thinning fluid droplets impinging on a hydrophobic surface (equilibrium contact angle θeq ≈ 108°and contact angle hysteresis Δθ ≈ 20°) have been studied experimentally and numerically. The impact processes of Newtonian fluid droplets with various viscosities and non-Newtonian fluid droplets with dilute xanthan gum solutions were recorded by a high-speed imaging system under a range of Weber numbers (We) from 12 to 208. A numerical model of the droplet impact on the solid substrate was also constructed using a finite element scheme with the phase field method (PFM). The experimental results show that unlike the Newtonian fluid droplets where either partial rebound or deposition occurs, complete rebound behavior was observed for non-Newtonian fluid droplets under a certain range of We. Moreover, the minimum value of We required for complete rebound increases with xanthan concentration. The numerical simulations indicate that the shear-thinning property significantly affects the rebound behavior of the droplets. As the amount of xanthan increases, the high shear rate regions shift to the bottom of the droplet and the receding of the contact line accelerates. Once the high shear rate region appears only near the contact line, the droplet tends to fully rebound even on a hydrophobic surface. Through the impact maps of various droplets, we found that the maximum dimensionless height Hmax* of the droplet increases almost linearly with We as Hmax* ∼ αWe. In addition, a critical value Hmax, c* for the distinction between deposition and rebound for droplets on the hydrophobic surface has been theoretically derived. The prediction of the model shows good consistency with the experimental results.
研究领域:
流体力学
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材料科学
·
界面科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
EXPERIMENTAL THERMAL AND FLUID SCIENCE
·
2024
·
IF 2.8
Lijuan Qian,Liujun Xu,Chengbin Sun,Li Lv
The surface and droplet characteristics significantly affect the dynamic of droplet impact on solid surfaces. In present work, a platform is utilized to experimentally study the dynamic behavior of shear thinning fluid droplets impacting superhydrophobic spheres, where the effects of different concentrations, Weber numbers ( We ), particle size ratios on droplets impact are studied. The results showed that on the superhydrophobic sphere, as the shear thinning droplet concentration increases, the diffusion diameter increases, and the contact time decreases. For the same curvature, the contact time between the droplet and the sphere decreases with the increase of the We . When the We reaches 75 or above, the contact time remains constant with an increase in the We . For various curvature conditions, the contact time increases as the curvature increasing. When the diameter ratio of the sphere to the droplet is D ∗ ≥ 6 , the maximum diffusion coefficient remains almost constant. However, when D ∗ < 6 , the maximum diffusion dimensionless diameter significantly increases as the particle size ratio decreases. More importantly, a theoretical model considering gravity effect is presented to predict the maximum dimensionless diameter of shear thinning droplets on superhydrophobic spheres according to energy conservation. The predicted results are rationally agreement with experiments with the deviation within ±10 %.
研究领域:
流体力学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
KOREA-AUSTRALIA RHEOLOGY JOURNAL
·
2024
·
IF 2.2
Yang Ding,Chen Jiaqi,Shen Ao,Wang Junfeng,Liu Hailong
The spreading behavior of droplets impacting solid surfaces is of significant importance in numerous industrial and medical applications. This study specifically focuses on the droplet impact behaviors of shear-thinning fluids. Extensive impact experiments were conducted using high-speed visualization techniques. Image sequences in the DI water and xanthan gum solution droplets impact process are captured at a We range of around 3.2–388 and Re n of 18–8145. The morphologies of spreading droplets on hydrophilic, moderate, and hydrophobic surfaces was observed with temporal evolution. The experimental results showed that the spreading behavior of shear-thinning droplets varies with the impact velocity, surface wettability, and fluid concentration. The droplets spread more widely and rapidly at larger We with the time evolution of the spreading factor. In addition, the spreading of the droplets becomes suppressed on a hydrophobic surface or with a higher xanthan concentration. With the increase of We , the effect of fluid viscosity gradually surpasses the surface wettability. The fluid viscosity with the shear-thinning properties has more influence on the spreading behavior at high We . Furthermore, the experimental data of the maximum spreading factor could be scaled with the We and Re n at low and high We , respectively. Finally, the maximum spreading of shear-thinning droplets was correlated with a universal rescaling model. The correlation shows good accordance with the experimental results of droplet impact from this study and the literature in a wide range of impact conditions and shear-thinning properties. Graphical abstract
研究领域:
流体力学
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材料科学
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工程学
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2025
·
IF 3.9
Bing Xiang,Kefeng Fang,Runci Song,Xinyi Chen,Kaihui Cui,Guoqing Zeng,Jie Chen,Xin Feng,Chao Yang
Understanding the behavior of surfactant-laden droplets impacting superhydrophobic surfaces is critical for various industrial applications. However, the influence of surfactant hydrophobic chain lengths (HCLs), which affect the diffusion coefficient of surfactants, on impact dynamics and predictive model for the maximum spreading diameter of surfactant droplets impacting superhydrophobic surfaces remain poorly understood, particularly under varying Weber numbers (We) and concentrations. This study experimentally investigates the impact dynamic of surfactant-loaded droplets with differing HCLs, focusing on their spreading, maximum spreading diameter, retraction, and oscillation behaviors. A key finding is that surfactants primarily enhance droplet deposition by inhibiting retraction stage. The deposition-enhancing effect exhibits an initial increase and subsequent decrease with increasing HCLs, governed by the interplay between dynamic surface tension, diffusion coefficient, and viscosity. Additionally, moderate increases in We favor droplet deposition and enhanced damping effect for surfactant-laden droplets impacting superhydrophobic surfaces. Finally, introducing the diffusion coefficient of surfactant through the Peclet number creates a generalized model to accurately predict the maximum spreading diameter of different surfactant droplets impacting superhydrophobic surfaces in varying impact velocities. This can be expressed as follows: βmax = 0.55Pe–0.017Re0.0679We0.246. These insights offer a deeper understanding of surfactant-laden droplet behavior on superhydrophobic surfaces and provide strategies for optimizing deposition in practical applications.
研究领域:
流体力学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
KOREA-AUSTRALIA RHEOLOGY JOURNAL
·
2019
·Vol. 31
·期 3
·167-177
·
IF 1.354
Liu Hai Long,Shen Xuefeng,Wang Rui,Huo Yuanping,Li Changfeng,Wang Junfeng
In this work, the impact dynamics of high-viscous nanofluid droplets onto a solid surface has been investigated experimentally by means of high-speed camera visualization technique. We dispersed various nanoparticles (multiwall carbon nanotube (MWCNT), nano-graphene, and nano-graphite powder) into high-viscous base fluid (epoxy resin) to obtain the stable and homogenous nanofluids without surfactant additives. The well dispersed nanofluids show different degree of shear-thinning behaviors, and the shear-thinning properties of those fluids have been characterized by the power-law rheology model. The dynamic contact angle (DCA), transient dimensionless height, and transient contacting factor along with the spreading time under different Weber numbers (We) have been investigated. The results show that the nanofluid with a lower shear viscosity over the entire range of the shear rates results in larger variations of the contacting factor and the dimensionless height. The effect of surface wettability on droplet impact behaviors is more significant for the fluid with higher shear viscosity and less shear-thinning degree during the receding phase. The latter spreading and receding motions of the droplet with higher shear viscosity and shear-thinning degree are suppressed significantly, regardless of the Weber numbers in current study. Finally, a model based on experimental data has been proposed to predict the maximum spreading factor of high-viscous droplet impact on solid surface.
研究领域:
流体力学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
Coatings
·
2023
·Vol. 13
·期 2
·264
·
IF 3.4
Bo Li,Lei Fan,Jie Bai,Huiying Xiang,Yuan Yuan
The dynamic behaviors of water droplets on a slippery surface are significant to practical anti-icing applications. Herein, the impact and sliding behavior of water droplets on lubricant-infused surfaces (LISs) were investigated with a high-speed camera. LISs were prepared by infusing perfluoropolyether oils into anodized porous surfaces. The results show that the maximum spreading diameter and retraction velocity of the impact droplet increased with theWenumber. For LIS-100, the spreading factor at 2.5 ms increased from 2.00 to 3.88 withWeincreasing from 30 to 267. Low-viscosity lubricant facilitated the retraction speed and rebound of droplet impact on the surface, while high-viscosity lubricant contributed to the lubricant stability of the LIS. Additionally, high inclination angle (θ) facilitated the rapid shedding of water droplets on the surface. The velocity increased rapidly from 1.04 to 4.66 mm/s withθincreasing from 15° to 45°. The LIS prepared with low-viscosity lubricant had a high sliding velocity, and the sliding velocity of water droplets on LIS-100 was about seven times faster than that on LIS-104. This work reveals the impacting law of water droplets on LISs and provides useful information for the design of LISs under drop impact conditions.Keywords:impact behavior;Wenumbers;surface inclinations;slippery surface
研究领域:
材料科学
·
流体力学
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
·
2022
·
IF 5.431
Gudlavalleti VVS Vara Prasad,Purbarun Dhar,Devranjan Samanta
In this article, a novel method of increasing the dynamic Leidenfrost temperature T DL is proposed by adding both anionic (SDS) and cationic (CTAB) surfactants to water droplets. We focus on understanding the hydrodynamics and thermal aspects of droplet impact Leidenfrost behavior of surfactant solutions and aim to delay the onset of the Leidenfrost regime. The effects of Weber number ( We ), Ohnesorge number ( Oh ), and surfactant concentration on dynamic Leidenfrost temperature ( T DL ) were experimentally studied in detail, covering a wide gamut of governing parameters. At a fixed impact velocity, T DL was increased with increase of surfactant concentration. T DL decreased with the increase of impact velocity for all solutions of surfactant droplets at a fixed surfactant concentration. We proposed a scaling relationship for T DL in terms of We and Oh. At temperatures (∼ 400 °C) considerably higher than T DL , droplets exhibit trampoline-like dynamics or central jet formation, associated with fragmentation, depending upon the impact velocity. Finally, a regime map of the different boiling regimes such as transition boiling, Leidenfrost effect, trampolining, and explosive behavior was presented as a function of impact We and substrate temperature ( T S ). The findings may hold substantial implications in thermal management systems operating at high temperatures.
研究领域:
热力学
·
流体力学
✓ 已验证
DOI
高影响因子
Fluids
·
2025
·Vol. 10
·期 6
·144
·
IF 1.8
Yuanjie Chen,Yucai Lin,Shile Feng,Yongmei Zheng
Superhydrophobic surfaces with a low liquid–solid contact time have huge application prospects in anti-icing, corrosion-resistant, self-cleaning, etc. Significant attempts have been devoted to reducing the contact time through altering the hydrodynamics of the process through which the droplet contacts the superhydrophobic surface. However, these works are rarely considered to be related to the influence of environmental conditions (e.g., the pH of the droplet, salinity of the droplet, droplet viscosity, and supercooled droplet impact). Here, we report various superhydrophobic cone arrays (SCAs) with low droplet impact contact times under various conditions (pH of the droplet, salinity of the droplet, droplet viscosity, droplet temperature, etc.). We demonstrate that the low contact time of the droplet impacting cone-arrays can be optimized via the critical Weber number, pillar-to-pillar spacing, and pillar height (e.g., 11.1, 350 μm, and 300 μm, respectively). The lowest droplet contact time of ~6 ms, which is reduced by more than 60% compared to conventional bouncing, can be achieved. In addition, directional pancake bouncing behaviors can achieve the largest horizontal displacement (85% of the droplet size, ~3 mm) on a tilted SCA with optimal tilt angles. These findings offer insights into the interface effect for controlling wetting that would extend the practical applications, e.g., liquid repellency, anti-corrosion, anti-icing, heat transfer, etc.
研究领域:
材料科学
·
表面工程
·
流体力学
·
应用物理
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY
·
2023
·
IF 2.2
Zhiwen Chen,Xiaoyong Yang,Bingjie Wang,Jian Dai,Zhishan Bai
Plate separators are widely used for oil-water separation in the petrochemical industry. The microscopic adhesion behavior of oil droplets at the solid surface is the key to understanding the oil-water separation mechanism in the plate separator. However, published microscopic experiments and mechanism research is insufficient. This study experimentally investigates the process of oil droplets impacting solid surfaces of Polytetrafluoroethylene (PTFE), 304 stainless steel, and Polyvinyl chloride using a high-speed camera. The influences of solid surfaces with different wettability and inclined angles from 0° to 45° are studied. The results show that oil droplets have the shortest drainage time and the greatest spreading speed on PTFE plates. The drainage time on an inclined surface is significantly longer than on a horizontal plate, and increases as the angle increases. The maximum spreading length occurs at an inclined angle of 15°, and is less affected by the angle as the Weber number (We) decreases. This study facilitates the understanding of oil droplet adhesion on a coalescing material surface in a plate separator from a microscopic view.
研究领域:
化学工程
·
材料科学
·
环境工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）