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 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 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

scholarly journals Droplet impact on flowing liquid films with inlet forcing: the splashing regime

Soft Matter ◽  
2017 ◽  
Vol 13 (41) ◽  
pp. 7473-7485 ◽  
Author(s):  
Idris T. Adebayo ◽  
Omar K. Matar
Keyword(s):  
Liquid Films ◽  
Drop Impact ◽  
Droplet Impact ◽  
Impact Dynamics ◽  
Spatial Structures ◽  
P Waves ◽  
Flowing Liquid ◽  
The Impact

Waves! Spatial structures on flowing liquid films contribute immensely to drop impact dynamics and notably alter the impact outcomes.

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.

Molecular-Scale Reagent Transport-Induced Modification of Low Weber Number Droplet Impact Dynamics

2007 ◽  
Author(s):  
Kalpak P. Gatne ◽  
Raj M. Manglik ◽  
Milind A. Jog
Keyword(s):  
High Speed ◽  
Surfactant Concentration ◽  
Water Drop ◽  
Pure Water ◽  
Sodium Dodecyl ◽  
Hydrophobic Surface ◽  
Video Camera ◽  
Impact Dynamics ◽  
Dynamic Surface ◽  
The Impact

Effect of surfactant molecular mass transport on the normal impact and spreading of a droplet of its aqueous solution on dry horizontal substrates is investigated for a range of Weber numbers (We = 20 – 100). The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 4000 frames per second. Digital image-processing software was used to determine the drop spread and height of the liquid film on the surface from each frame. Experiments were performed with water and with two different aqueous solutions of Sodium Dodecyl Sulphate (SDS), one at its half critical micelle concentration (CMC) and another at twice CMC, on a hydrophilic surface (glass) and a hydrophobic surface (Teflon). It is seen that surfactant concentration, its dynamic surface tension behavior, and surface wettability govern the transient impact-spreading-recoil phenomena. A droplet of SDS solution exhibits higher maximum spread and weaker surface oscillations compared to a pure water drop colliding with the same velocity. On a hydrophobic (Teflon) surface, the drop rebound is inhibited by the presence of the surfactant. These effects are more pronounced at surfactant concentration of twice CMC compared to that at half CMC.

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.

Drop Impact Dynamics: Impact Force and Stress Distributions

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Xiang Cheng ◽  
Ting-Pi Sun ◽  
Leonardo Gordillo
Keyword(s):  
High Speed ◽  
Impact Force ◽  
Drop Impact ◽  
Impact Dynamics ◽  
Annual Review ◽  
Publication Date ◽  
High Speed Photography ◽  
Stress Distributions ◽  
Wide Range ◽  
The Impact

Dynamic variables of drop impact such as force, drag, pressure, and stress distributions are key to understanding a wide range of natural and industrial processes. While the study of drop impact kinematics has been in constant progress for decades thanks to high-speed photography and computational fluid dynamics, research on drop impact dynamics has only peaked in the last 10 years. Here, we review how recent coordinated efforts of experiments, simulations, and theories have led to new insights on drop impact dynamics. Particularly, we consider the temporal evolution of the impact force in the early- and late-impact regimes, as well as spatiotemporal features of the pressure and shear-stress distributions on solid surfaces. We also discuss other factors, including the presence of water layers, air cushioning, and nonspherical drop geometry, and briefly review granular impact cratering by liquid drops as an example demonstrating the distinct consequences of the stress distributions of drop impact. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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.

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