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

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.

Effects of Surface Tension on Drop Impact on a Horizontal Rotating Disk

2012 ◽  
Vol 268-270 ◽  
pp. 1084-1093
Author(s):  
Xiao Fang Yuan ◽  
Jing Yin Li ◽  
Bin Zhang
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Tangential Velocity ◽  
Rotating Disk ◽  
Lower Surface ◽  
Drop Impact ◽  
Experimental Results ◽  
Impact Processes ◽  
Lower Surface Tension ◽  
The Impact

The impact processes of water and ethanol drops on a rotating horizontal aluminum disk were recorded and analyzed using a high-speed digital camera together with an image analysis program. The angular velocities of the disk were altered to study the effect of surface tension of drops on drop impact processes. The experimental results show that a lower surface tension will result in a higher tangential spread factor and a lower receding rate during the receding stage, for the drop impinging and depositing on a rotating disk. In addition, a lower surface tension of the drop tends to promote the occurrence of splash. The experimental results further verify a proposed correlation of splash-deposition boundary for drops impinging on a rotating disk. Both drops, though they have a quite different surface tension, experience four stages, with two new stages different from those of drops impinging on stationary surfaces. Their tangential spreading factors both increase obviously with the tangential velocity at the impact point, while their radial spreading factors vary a little.

Experiments on the breakup of drop-impact crowns by Marangoni holes

2018 ◽  
Vol 844 ◽  
pp. 162-186 ◽  
Author(s):  
Abdulrahman B. Aljedaani ◽  
Chunliang Wang ◽  
Aditya Jetly ◽  
S. T. Thoroddsen
Keyword(s):  
Surface Tension ◽  
Lower Surface ◽  
High Viscosity ◽  
Solid Substrate ◽  
Immiscible Liquid ◽  
Hole Formation ◽  
Low Viscosity ◽  
Stress Changes ◽  
Lower Surface Tension ◽  
The Impact

We investigate experimentally the breakup of the Edgerton crown due to Marangoni instability when a highly viscous drop impacts on a thin film of lower-viscosity liquid, which also has different surface tension than the drop liquid. The presence of this low-viscosity film modifies the boundary condition, giving effective slip to the drop along the solid substrate. This allows the high-viscosity drop to form a regular bowl-shaped crown, which rises vertically away from the solid and subsequently breaks up through the formation of a multitude of Marangoni holes. Previous experiments have proposed that the breakup of the crown results from a spray of fine droplets ejected from the thin low-viscosity film on the solid, e.g. Thoroddsen et al. (J. Fluid Mech., vol. 557, 2006, pp. 63–72). These droplets can hit the inner side of the crown forming spots with lower surface tension, which drives a thinning patch leading to the hole formation. We test the validity of this assumption with close-up imaging to identify individual spray droplets, to show how they hit the crown and their lower surface tension drive the hole formation. The experiments indicate that every Marangoni-driven patch/hole is promoted by the impact of such a microdroplet. Surprisingly, in experiments with pools of higher surface tension, we also see hole formation. Here the Marangoni stress changes direction and the hole formation looks qualitatively different, with holes and ruptures forming in a repeatable fashion at the centre of each spray droplet impact. Impacts onto films of the same liquid, or onto an immiscible liquid, do not in general form holes. We furthermore characterize the effects of drop viscosity and substrate-film thickness on the overall evolution of the crown. We also measure the three characteristic velocities associated with the hole formation: i.e. the Marangoni-driven growth of the thinning patches, the rupture speed of the resulting thin films inside these patches and finally the growth rate of the fully formed holes in the crown wall.

scholarly journals Lifting a sessile oil drop from a superamphiphobic surface with an impacting one

2020 ◽  
Vol 6 (34) ◽  
pp. eaba4330
Author(s):  
Olinka Ramírez-Soto ◽  
Vatsal Sanjay ◽  
Detlef Lohse ◽  
Jonathan T. Pham ◽  
Doris Vollmer
Keyword(s):  
Surface Tension ◽  
Energy Transfer ◽  
Impact Velocity ◽  
Sessile Drop ◽  
Cloud Formation ◽  
Impact Dynamics ◽  
Combustion Engines ◽  
Intrinsic Properties ◽  
Natural Processes ◽  
The Impact

Colliding drops are encountered in everyday technologies and natural processes, from combustion engines and commodity sprays to raindrops and cloud formation. The outcome of a collision depends on many factors, including the impact velocity and the degree of alignment, and intrinsic properties like surface tension. Yet, little is known on binary impact dynamics of low-surface-tension drops on a low-wetting surface. We investigate the dynamics of an oil drop impacting an identical sessile drop sitting on a superamphiphobic surface. We observe five rebound scenarios, four of which do not involve coalescence. We describe two previously unexplored cases for sessile drop liftoff, resulting from drop-on-drop impact. Numerical simulations quantitatively reproduce the rebound scenarios and enable quantification of velocity profiles, energy transfer, and viscous dissipation. Our results illustrate how varying the offset from head-on alignment and the impact velocity results in controllable rebound dynamics for oil drop collisions on superamphiphobic surfaces.

Experimental Investigation of Droplet Dynamics on Solid Surfaces: Spreading and Recoil Effects

2006 ◽  
Author(s):  
Kalpak P. Gatne ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Lower Surface ◽  
Video Camera ◽  
Temporal Variations ◽  
Liquid Viscosity ◽  
Viscous Effects ◽  
Droplet Dynamics ◽  
Digital Video Camera ◽  
The Impact

A study of the normal impact of liquid droplets on a dry horizontal substrate is presented in this paper. The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 2000 frames per second. A digital image processing software was used to determine the drop spread and height of the liquid on the surface from each frame. To ascertain the effects of liquid viscosity and surface tension, experiments were conducted with four liquids (water, ethanol, propylene glycol and glycerin) that have vastly different fluid properties. Three different Weber numbers (20, 40, and 80) were considered by altering the height from which the drop is released. The high-speed photographs of impact, spreading and recoil are shown and the temporal variations of dimensionless drop spread and height are provided in the paper. The results show that changes in liquid viscosity and surface tension significantly affect the spreading and recoil behavior. For a fixed Weber number, lower surface tension promotes greater spreading and higher viscosity dampens spreading and recoil. Using a simple scale analysis of energy balance, it was found that the maximum spread factor varies as Re1/5 when liquid viscosity is high and viscous effects govern the spreading behavior.

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.

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.

The Impact of Liquid Surface Tension on Fabric Drying Efficiency

2012 ◽  
Vol 441 ◽  
pp. 613-618 ◽  
Author(s):  
Ji Li Tu ◽  
Chun Jie Qian ◽  
Hua Yun Ge ◽  
Ji Ping Wang ◽  
Jin Qiang Liu
Keyword(s):  
Surface Tension ◽  
Water Retention ◽  
Liquid Surface ◽  
Lower Surface ◽  
Liquid Surface Tension ◽  
Lower Surface Tension ◽  
Dehydration Processes ◽  
Drying Efficiency ◽  
The Impact ◽  
The Relationship

This study presents an experimental investigation of the relationship between liquid surface tension and fabrics water retention in dehydration processes such as centrifuging, line drying and heat drying. Selected surfactants were used to prepare wash baths with different surface tension, and dehydrating experiments of cotton fabric after immersion in above bath were conducted. The results showed that lower surface tension is beneficial to reducing fabrics water retention by centrifuging and improving line drying efficiency and heat drying efficiency. It was assumed that water with low surface tension is easy to drop down or separate from fabric, thus improving the de-watering and drying efficiency.

The role of viscosity and surface tension in bubble entrapment during drop impact onto a deep liquid pool

2007 ◽  
Vol 578 ◽  
pp. 119-138 ◽  
Author(s):  
Q. DENG ◽  
A. V. ANILKUMAR ◽  
T. G. WANG
Keyword(s):  
Surface Tension ◽  
Capillary Number ◽  
High Speed ◽  
Impact Crater ◽  
Pure Water ◽  
Cone Angle ◽  
Drop Impact ◽  
Inviscid Limit ◽  
Main Body ◽  
The Impact

The phenomenon of liquid drop impact onto the surface of a deep pool of the same liquid is studied in the context of bubble entrapment, using high-resolution digital photography. Three liquids, pure water, glycerin/water mixtures, and silicon oil, have been used to investigate the effect of viscosity (μ) and surface tension (σ) on regular bubble entrapment, and the associated impact crater signatures. The global viscous effect is seen as a shift in the classical inviscid bubble entrapment limits, whereas, at the impact crater, the local effect is seen as a weakening of the capillary wave, which is responsible for bubble pinching, and a weakening of the intensity of crater rebound. Bubble entrapment, which results from a competition between concentric capillary pinching of the crater cusp and viscous damping, is captured well by the capillary number Ca (Ca = mu Viσ, where Vi is the drop impact velocity). The measured peak entrapped bubble size decreases exponentially as capillary number increases, with the cut-off capillary number for bubble entrapment estimated to be around 0.6. The critical crater cone angle for peak bubble pinch-off weakly increases with capillary number, with the measured value in agreement with theory in the inviscid limit (low Ca). Additionally, the growth of the main body of the high-speed thin jet, formed immediately following bubble pinch-off, is fitted to a power-law singularity model. This suggests that the thin jet is similar to the hydraulic jets produced by the collapse of free-surface standing waves.

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