Two types of Cassie-to-Wenzel wetting transitions on superhydrophobic surfaces during drop impact

Soft Matter ◽  
2015 ◽  
Vol 11 (23) ◽  
pp. 4592-4599 ◽  
Author(s):  
Choongyeop Lee ◽  
Youngsuk Nam ◽  
Henri Lastakowski ◽  
Janet I. Hur ◽  
Seungwon Shin ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Water Drop ◽  
Drop Impact ◽  
Superhydrophobic Surfaces ◽  
Wetting Transitions ◽  
Different Types ◽  
The Impact

Different types of Cassie-to-Wenzel transitions on superhydrophobic surfaces with the impact velocity of water drop.

scholarly journals Experimental Study of Drop Impact on Deep-Water Surface in the Presence of Wind

2018 ◽  
Vol 48 (2) ◽  
pp. 329-341 ◽  
Author(s):  
Xinan Liu
Keyword(s):  
Deep Water ◽  
Water Surface ◽  
Water Drop ◽  
Threshold Value ◽  
Impact Angle ◽  
Drop Impact ◽  
Wind Speeds ◽  
Secondary Droplets ◽  
Low Wind Speeds ◽  
The Impact

AbstractThe effects of wind on the impact of a single water drop on a deep-water surface are studied experimentally in a wind tunnel. Experiments are performed by varying impacting drop diameters, ranging from 2.5 to 4.1 mm and wind speeds up to 6.7 m s−1. The sequence of splashing events that occurred during drop impacts is recorded with a backlit, cinematic shadowgraph technique. The experimental results show that for low wind speeds, an asymmetrical crown forms on the leeward of the periphery of the colliding region after the drop hits the water surface, while a wave swell forms on the windward. Secondary droplets are generated from the crown rim. For high wind speeds with large drop diameters, ligaments are generated from the crown rim on the leeward of the drop impact site. The ligaments grow, coalesce, and fragment into secondary droplets. It is found that both the drag force and surface tension play important roles in the evolution process of the ligaments. The nondimensional K number (K = WeOh−0.4, where We is the Webber number and Oh is the Ohnesorge number) is used to describe the splashing-deposition limit of drop impact. The threshold value of this K number changes with the wind velocity and/or drop impact angle.

scholarly journals Drop Impact on Textile Material: Effect of Fabric Properties

2014 ◽  
Vol 14 (3) ◽  
pp. 145-151 ◽  
Author(s):  
Zouhaier Romdhani ◽  
Ayda Baffoun ◽  
Mohamed Hamdaoui ◽  
Sadok Roudesli
Keyword(s):  
Water Drop ◽  
Free Fall ◽  
Spreading Rate ◽  
Drop Impact ◽  
Drop Deformation ◽  
Coating Film ◽  
Drop Shape ◽  
Coated Fabric ◽  
Fabric Construction ◽  
The Impact

Abstract This paper presents an experimental study of impact of water drop on a surface in a spreading regime with no splashing. Three surfaces were studied: virgin glass, coating film and woven cotton fabric at different construction parameters. All experiments were carried out using water drop with the same free fall high. Digidrop with high-resolution camera is used to measure the different parameters characterising this phenomenon. Results show an important effect of the height of the free fall on the drop profile and the spreading behaviour. An important drop deformation at the surface impact was observed. Then, fabric construction as the weft count deeply affects the drop impact. For plain weave, an increase of weft count causes a decrease in penetration and increase in the spreading rate. The same result was obtained for coated fabric. Therefore, the impact energy was modified and the drop shape was affected, which directly influenced the spreading rate.

scholarly journals Drop impact dynamics on slippery liquid-infused porous surfaces: influence of oil thickness

Soft Matter ◽  
2018 ◽  
Vol 14 (7) ◽  
pp. 1100-1107 ◽  
Author(s):  
M. Muschi ◽  
B. Brudieu ◽  
J. Teisseire ◽  
A. Sauret
Keyword(s):  
Water Drop ◽  
Drop Impact ◽  
Impact Dynamics ◽  
Porous Surfaces ◽  
The Impact ◽  
Oil Thickness

This paper investigates the impact dynamics of a water drop on slippery liquid-infused surfaces of varying oil thickness.

scholarly journals Exploring droplet impact near a millimetre-sized hole: comparing a closed pit with an open-ended pore

2015 ◽  
Vol 772 ◽  
pp. 427-444 ◽  
Author(s):  
Rianne de Jong ◽  
Oscar R. Enríquez ◽  
Devaraj van der Meer
Keyword(s):  
Impact Velocity ◽  
Crucial Role ◽  
Drop Impact ◽  
Impact Dynamics ◽  
Air Bubbles ◽  
Air Bubble ◽  
Impact Location ◽  
Impact Phenomena ◽  
The Impact

We investigate drop impact dynamics near closed pits and open-ended pores experimentally. The resulting impact phenomena differ greatly in each case. For a pit, we observe three distinct phenomena, which we denote as a splash, a jet and an air bubble, whose appearance depends on the distance between impact location and pit. Furthermore, we found that splash velocities can reach up to seven times the impact velocity. Drop impact near a pore, however, results solely in splashing. Interestingly, two distinct and disconnected splashing regimes occur, with a region of planar spreading in between. For pores, splashes are less pronounced than in the pit case. We state that, for the pit case, the presence of air inside it plays the crucial role of promoting splashing and allowing for air bubbles to appear.

scholarly journals Drop Impact onto a Metallic Porous Layer: Effect of Liquid Viscosity and Air Entrapment

2017 ◽  
Author(s):  
Cristina Boscariol ◽  
Dipak Sarker ◽  
Boseon Kang ◽  
Cyril Crua ◽  
Marco Marengo
Keyword(s):  
Surface Tension ◽  
Pore Size ◽  
Impact Velocity ◽  
Lower Surface ◽  
Deposition Process ◽  
Drop Impact ◽  
Theoretical Modelling ◽  
Glycerol Solution ◽  
Porous Surfaces ◽  
The Impact

The drop impact onto porous surfaces has important applications in many fields, such as painting, paper coating,drug delivery and cosmetic sprays. In most of these applications, the optimisation of the deposition process is carried out empirically, without a proper understanding of the physics and a theoretical modelling of the spreading and the imbibition phenomena. The purpose of this study is to analyse droplet impacts on metallic meshes to define a general modelling strategy of the impact regimen on particular 2D regular porous surfaces. The application of this structure is relevant in process like filtration but also in the medical field, considering for example reconstructive surgery. By analysing the impact of droplets of water, acetone and a mixture of glycerol and water, having a diameter and an impact velocity in a range of 1.5-3mm and 2-4m/s, respectively, on meshes with a pore size ranging between 25 and 400 µm, a regime map was built considering 6 different impact outcomes. The outcomes were characterised by a deposition of the droplet on the substrate, or a partial imbibition, or a total imbibition. By increasing the impact velocity, a splash region was defined, which is still characterised by a final deposition, a partial imbibition and a total imbibition. It is found that the most influencing parameters are closely linked to the liquid properties and the impact velocity, more specifically liquid surface tension plays a major role in defining the impact outcome. In the case of Acetone, the lower surface tension brings to an almost instantaneous total imbibition whereas the experiments conducted using water and glycerol solution, showed a major distribution of the deposition regimes with respect to the other outcomes, due to the effect of a higher viscosity. It was found that the geometrical characteristics of the mesh such as pore size and wire diameter, play an important role as well in defining the total imbibition outcome. Finally, the defined transition maps, shows that for a certain combination of physical properties and initial condition,the outcome of the droplet impact is predictable.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4973

Irregular Bubble Entrainment Following Drop Impact on a Free Surface

2003 ◽  
Author(s):  
Yukio Tomita ◽  
Toshiyasu Kasai ◽  
Shinya Miura
Keyword(s):  
Free Surface ◽  
Impact Velocity ◽  
Water Surface ◽  
Drop Impact ◽  
Drop Diameter ◽  
Air Bubbles ◽  
Air Bubble ◽  
Bubble Entrainment ◽  
Irregular Case ◽  
The Impact

An air bubble is entrained by the impact of a drop on a water surface. Consequently sound is emitted. There are two categories of the bubble entrainment depending on the drop diameter dD and impact velocity Vimp. One is the regular entrainment where air bubbles are always pinched off, another is the irregular case where bubbles are trapped irregularly. In this paper we explore the mechanism of the irregular bubble entrainment and induced bubble sound.

3D Simulation of Drop Impact on Dry Surface Using SPH Method

2018 ◽  
Vol 15 (03) ◽  
pp. 1850011 ◽  
Author(s):  
Xiufeng Yang ◽  
Song-Charng Kong
Keyword(s):  
Surface Tension ◽  
Impact Velocity ◽  
Free Particle ◽  
Particle Method ◽  
Drop Impact ◽  
Sph Method ◽  
Spherical Drop ◽  
Mesh Free ◽  
Particle Hydrodynamics ◽  
The Impact

The purpose of this paper is to present and illustrate a smoothed particle hydrodynamics (SPH) method to study the process of a drop impacting on a dry solid surface. SPH is a Lagrangian mesh-free particle method that offers advantages in modeling the evolution of the liquid surface during drop impact. A new surface tension model is used. The artificial viscosity is also used, which is demonstrated to be, approximately, a linear function of the dynamic viscosity of the liquid. The SPH method is used to simulate different liquid drops impacting on dry surfaces. The numerical results agree with experimental data obtained from the literature. The influence of various parameters on the drop impact, including impact velocity, diameter, viscosity, surface tension, and density of the drop, is also studied. The results show that the dimensionless spreading diameter of the drop increases if the impact velocity, diameter, or density increases, while the increase in viscosity and surface tension decreases the spreading diameter. The results indicate that the drop impact depends more strongly on the viscosity and impact velocity than on the diameter, surface tension, and density of the drop. In addition to the impact of a spherical drop, the impact of an ellipsoidal drop on a dry surface is also studied. The results show that the aspect ratio of the drop has a significant influence on the outcome of drop impact.

Impact patterns and temporal evolutions of water drops impinging on a rotating disc

2011 ◽  
Vol 226 (4) ◽  
pp. 956-967 ◽  
Author(s):  
J-Y Li ◽  
X-F Yuan ◽  
Q Han ◽  
G Xi
Keyword(s):  
High Speed ◽  
Water Drop ◽  
Video Camera ◽  
Drop Impact ◽  
Rossby Number ◽  
Rotating Disc ◽  
Factors Affecting ◽  
Radial Spread ◽  
Spread Factor ◽  
The Impact

The impact process of a water drop colliding with a rotating disc was recorded and analysed using a high-speed video camera. Four falling velocities of the drop, eight rotational speeds, and four impacting radii of the disc were chosen to study their influences on the outcomes of drop impact. The correlation of the deposition–splash boundary was found to be the function of Reynolds number, Weber number, and Rossby number. Four kinds of impact processes were classified in terms of Rossby number and several new stages of the impact outcomes not present in drop impact on a stationary plate were recognized. For deposition processes, the temporal evolutions of two spread factors, the tangential and radial spread factors, were analysed in detail. It was found that the Rossby number and the falling velocity of the drop are the major factors affecting the tangential spread factor. In contrast, the Rossby number has little effect on the radial spread factor while the falling velocity of the drop still exerts a considerable influence on it.

scholarly journals Theoretical and experimental study on mechanical characterisation of a water drop impact on a solid surface

2016 ◽  
Vol 47 (1) ◽  
pp. 12
Author(s):  
Luigi Cavazza ◽  
Adriano Guarnieri ◽  
Angelo Fabbri ◽  
Chiara Cevoli ◽  
Giovanni Molari
Keyword(s):  
Fine Particles ◽  
Solid Wall ◽  
Water Drop ◽  
Drop Impact ◽  
Impact Pressure ◽  
Theoretical Concepts ◽  
Average Percentage ◽  
Percentage Difference ◽  
Experimental Apparatus ◽  
The Impact

The drop impact phenomenon can be used to study many agricultural aspects related to the rainfall, runoff and irrigation, such as the stability of aggregated and the detachment of fine particles. The aim of this study was to study experimentally and numerically the water drop impact on a solid wall. In a first phase a simple experimental apparatus and basic theoretical concepts were used to investigate the influence of the drop speed on the impact pressure. In the second section, a finite element model able to reproduce the complex phenomenon observed in the experimental phase, was developed. The pressure values obtained by experimental measurement are similar to those calculated on the base of the energy conservation principle (average percentage difference of 15.6%). Numerical model was useful to obtain important information on pressure profile inside the drop and the impact pressure during the splash, at present hard to achieve experimentally. The model was used to estimate also an almost realistic dynamic behaviour of the spreading drop.

Determination of the effectiveness of high-speed cameras for identifying ejection particles during splash with regard to the sticky paper method

2020 ◽  
Author(s):  
Agata Sochan ◽  
Michał Beczek ◽  
Rafał Mazur ◽  
Magdalena Ryżak ◽  
Zbigniew Łagodowski ◽  
...  
Keyword(s):  
High Speed ◽  
Water Drop ◽  
Reference Method ◽  
Drop Impact ◽  
Glass Beads ◽  
Time Interval ◽  
Time Frequency ◽  
The Impact ◽  
Paper Method

<p>The phenomenon of splash caused by water drop has been widely studied in recent years. There are many measurement methods, including the method based on the use of so-called high-speed cameras. Due to the possibility of recording of the phenomenon with a high time frequency (thousands of recorded frames per second), this method provides detailed information about the process of splashed particles, which were previously unavailable. These include, among others, precise tracking of single ejected particles, determination of their ejection angle, displacement distance, and division of splashed elements into groups depending on the place or moment of ejection from the particle bedding. Despite the numerous advantages of the method, there is no information about the percentage of splashed particles that the cameras are able to detect and identify. In order to determine such effectiveness, it is necessary to have a reference method that guarantees 100% identification of splashed particles.</p><p>The aim of this work was to determine the effectiveness of high-speed cameras in identification of particles ejected from the granular bedding during the water drop impact. Sticky paper was used as a reference method.</p><p>Dry spherical glass beads (425–600 μm size range), which were placed into an aluminium ring (30mm diameter, 10mm height) were used in the experiments. The aluminum ring was placed in a drilled hole (only slightly larger than the ring) in a horizontal wooden plate, and therefore, the surface of the beads was at the same level as the surrounding plane. Drops (d=4.2mm) of distilled water were created in a peristaltic pump and fell free from 1.5m. The final velocity of each drop was 4.98 m/s.</p><p>Three synchronized Phantom Miro M310 cameras were used to register the splash phenomenon (307 μs time interval, 1280x800 px resolution). The camera calibration process facilitated analysis of the trajectories of the splashed particles and determination of their velocities, ejection angles, and displacement distances. The analysis of the recorded images was carried out using the Dantec Dynamics Studio software. The particles were tracked by the Volumetric 3DPTV module, and the trajectories were further analyzed by our script written in LabVIEW.</p><p>A hole (30mm diameter) was cut out of a piece of sticky paper, and the paper was placed concentrically over the ring. This allowed recording of all splashed particles while avoiding their rebounding or rolling from the plane. Following the impact, the beads were photographed using a Nikon D7100 camera, and images were analyzed using ImageJ software. The number of particles and the distance from the geometrical center of the drop impact were recorded.</p><p>Measurements using the high-speed cameras and the sticky paper method were carried out in 16 repetitions.</p><p>The results obtained with both methods were compared with each other. Regarding the sticky paper method as a reference, the efficiency of identification with the high-speed cameras for the splash of glass beads was determined, which was estimated at 53%.</p><p>The study was partially funded by the National Science Centre, Poland, in the frame of the project no. 2017/26/D/ST10/01026.</p>

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