Mili-Scale Visualization of Bubble Growth-Translation and Droplet Impact Dynamics

2006 ◽  
Vol 128 (8) ◽  
pp. 736-736 ◽  
Author(s):  
R. M. Manglik ◽  
M. A. Jog ◽  
A. Subramani ◽  
K. Gatne
Keyword(s):  
Surface Tension ◽  
Video Processing ◽  
High Speed ◽  
Digital Video ◽  
Capillary Tube ◽  
Droplet Impact ◽  
Stainless Steel Surface ◽  
Air Bubble ◽  
Processing Software ◽  
The Impact

The dynamic behavior of an air bubble, emanating from a 0.32 mm i.d., 0.64 mm o.d., vertical capillary-tube orifice with a bubble interval of 0.22–0.28 s at constant pressure and adiabatic (T=25°C) conditions, as well as droplet impact and spreading on a hydrophobic surface are characterized. Images of the mili-scale spatial-temporal evolution of bubbles (embryonic appearance at orifice tip → growth and detachment → translation) as well as droplets were acquired using a high-speed (5000 frames/s) digital video camera fitted with a 8× optical zoom lens. It was triggered through a computer interface to record continuous high-speed video from which any desired frame can be captured by digital-video-processing software; the equivalent departure diameter was estimated by area-averaging using image processing software. The impact, spreading, and recoil behaviors of ethanol and water droplets on a horizontal stainless steel surface are depicted in Fig. 1. For constant Weber number (We∼10), the spreading and recoil dynamics in the two cases are significantly different. Higher wettability of ethanol promotes greater spreading and dampens recoil in comparison with that seen in water. Figure 2 depicts the growth of an air bubble in pools of ethanol and water. While displaying similar ebullience, a bubble of smaller size and surface age is produced in low-surface-tension ethanol. Dynamic shape variations of the air bubble as it translates upwards in the pool are seen in Fig. 3. From a nearly spherical, tear-drop bubble, the shape changes to an oblate ellipsoid during translation, and surface tension effects are manifest only in the size of respective bubbles.

scholarly journals The effects of surface tension on the spreading ratio during the impact of multiple droplets onto a hot solid surface

2018 ◽  
Vol 197 ◽  
pp. 08016
Author(s):  
Rafil Arizona ◽  
Teguh Wibowo ◽  
Indarto Indarto ◽  
Deendarlianto Deendarlianto
Keyword(s):  
Surface Tension ◽  
Ethylene Glycol ◽  
Solid Surface ◽  
High Speed ◽  
Frame Rate ◽  
Stainless Steel Surface ◽  
Droplet Spreading ◽  
Secondary Droplets ◽  
The Impact ◽  
Maximum Spreading

The impact between multiple droplets onto hot surface is an important process in a spray cooling. The present study was conducted to investigate the dynamics of multiple droplet impact under various surface tensions. Here, the ethylene glycol with compositions of 0%, 5%, and 15% was injected through a nozzle onto stainless steel surface as the multiple droplet. The solid surface was heated at the temperatures of 100 °C, 150 °C, and 200 °C. To observe the dynamics of multiple droplets, a high speed camera with the frame rate of 2000 fps was used. A technique of image processing was developed to determine the maximum droplet spreading ratio. As the result, the surface tension contributes significantly to maximum spreading ratio. As the droplet surface tension decreases, the maximum spreading ratio increases. The maximum spreading ratio appears when the percentage of the ethylene glycol is 15% at the temperature of 150°C. From the visual observation, it is shown that a slower emergence of secondary droplets (droplet splashing) is carried out under a lower surface tension. Hence, surface tension plays an important role on the behavior of emerging secondary droplets. Furthermore, results of the experiments are useful for the validation of available previous CFD models.

Impact Tests in an Air-Water Mixture

2017 ◽  
Author(s):  
Aboulghit El Malki Alaoui
Keyword(s):  
High Speed ◽  
Volume Fraction ◽  
Optical Probe ◽  
Test Machine ◽  
Water Mixture ◽  
Air Bubble ◽  
Impact Tests ◽  
Void Fractions ◽  
Shock Test Machine ◽  
The Impact

Experimental impact tests were performed using a shock machine and aerated water by means of an air-bubble generator. High speed shock test machine allows carrying out tests of impact on water (slamming). This machine permits to stabilise velocity with a maximal error equal to 10% during slamming tests. The air volume fraction in the bubble was measured by optical probe technique. The present work is aimed at quantifying the effects of the aeration on the hydrodynamic loads and pressures during the entry of a rigid body at constant speed in an air-water mixture. The impact tests were conducted with a rigid pyramid for an impact velocity equal to 15 m.s−1 and for two average void fractions, 0,46% and 0,84%. The reduction of the impact force and pressure due to aeration has been confirmed by these experiments.

Numerical Analysis of Droplet Impact on a Smooth Slippery Surface

2018 ◽  
Author(s):  
F. Yeganehdoust ◽  
I. Karimfazli ◽  
A. Dolatabadi
Keyword(s):  
Droplet Impact ◽  
Immiscible Fluid ◽  
Oil Viscosity ◽  
Air Bubble ◽  
Air Cushion ◽  
Subsequent Effect ◽  
Interfacial Surfaces ◽  
The Stability ◽  
Moderate Range ◽  
The Impact

Spontaneous bouncing of a droplet that impacts a surface is a mechanism that occurs for the moderate range of droplet impact velocities and is caused by the formation of a stable air layer (cushion) between the droplet and the surface. This bouncing behavior is more pronounced on Lubricant Impregnated Surfaces (LISs) inspired by the natural non-wetting surface of the pitcher plant, which relies on the stable formation of a thin lubricant film across its surface. In this study, we performed modeling of the water-oil–air interfacial surfaces using the volume of fluid (VOF) methodology to simulate the impact of a water droplet onto a lubricant smooth surface with an oil as the lubricant. To resolve the effects of the air surrounding the droplet, computational cells were extensively small to capture the presence of the sub-micron layer of air trapped underneath the droplet during the impact. The model was able to capture the initiation and subsequent effect of the air cushion on the droplet hydrodynamics. We found that the stability of the air cushion and the impact dynamics are independent of the oil viscosity for specific thicknesses of lubricant layers, whereas the impact conditions such as velocity and droplet properties played a significant role on the outcome of droplet impact. Hence, the dynamics of a droplet falling on a specific thickness of oil film was influenced by the squeezed air trapped between the two immiscible fluid (water and oil). In addition, the formation of high pressure dimple region was evident, which in some cases lead to entrapment of the air bubble. Finally, we validated the results with the existing experimental data in the literature.

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 Short-term dynamics of a density interface following an impact

2007 ◽  
Vol 577 ◽  
pp. 241-250 ◽  
Author(s):  
A. ANTKOWIAK ◽  
N. BREMOND ◽  
S. LE DIZÈS ◽  
E. VILLERMAUX
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Liquid Velocity ◽  
Short Term ◽  
Liquid Surface Tension ◽  
Image Velocimetry ◽  
Interface Curvature ◽  
Impulse Pressure ◽  
The Impact ◽  
Wetting Liquid

A tube filled with a perfectly wetting liquid falls axially under its own weight. In its gravity-free reference frame, the liquid interface is deformed by surface tension into a hemispherical shape. On impact of the tube on a rigid floor, the interface curvature reverses violently, forming a concentrated jet. If the contact angle at the tube wall is such that the interface is flat, the liquid rebounds as a whole with the tube, with no deformation. We analyse this phenomenon using an impulse pressure description, providing an exact description of the initial liquid velocity field at the impact, supported by high-speed image velocimetry measurements. This initial dynamics is insensitive to liquid surface tension and viscosity.

Polychromatic Coloring of Dental Zirconia by Inkjet Printing

2019 ◽  
Author(s):  
Christoph Rehekampff ◽  
Dominik Rumschöttel ◽  
Franz Irlinger ◽  
Tim C. Lueth
Keyword(s):  
Surface Tension ◽  
Pore Size ◽  
Inkjet Printing ◽  
High Speed ◽  
Three Dimensional ◽  
Droplet Impact ◽  
High Speed Camera ◽  
Color Transition ◽  
Color Scale

Abstract To enable the development of an automated coloring process, dental zirconia is examined in terms of porosity, pore size and shrinkage during sintering. The properties of commercially available metal ionic inks such as viscosity, density and surface tension are investigated. Droplet impact on the zirconia surface and the absorption into the pores is analyzed with a high speed camera. The color result after sintering is investigated and compared to tooth samples. A method is developed to achieve a realistic, smooth color transition on flat zirconia samples. This is achieved by mixing the single inks directly on the zirconia through sequential application. Consequently, the number of different inks required to reproduce the full dental color scale can be reduced. Additionally, three dimensional tooth replacements are colored with the developed method.

scholarly journals Formation and rupture of gas film of antibubble

2020 ◽  
Vol 23 (1) ◽  
pp. 91-104
Author(s):  
Lichun Bai ◽  
Jinguang Sun ◽  
Zhijie Zeng ◽  
Yuhang Ma ◽  
Lixin Bai
Keyword(s):  
Liquid Film ◽  
High Speed ◽  
Liquid Surface ◽  
Single Layer ◽  
Liquid Films ◽  
Droplet Impact ◽  
Liquid Interface ◽  
High Speed Photography ◽  
Merging Process ◽  
The Impact

The formation and rupture of gas film in the process of formation, rupture and coalescence of antibubbles were investigated by high-speed photography. It was found that a gas film will appear and wrap a droplet when the droplet hit a layer of liquid film or foam before impacting the gas-liquid interface. The gas film may survive the impact on the gas-liquid interface and act as the gas film of an antibubble. A multilayer droplet will be formed when the droplet hits through several layer of liquid films, and a multilayer antibubble will be formed when the multilayer droplet impact a gas-liquid interface or a single layer of foam on the liquid surface. The way to generate antibubbles by liquid films will undergo the formation and rupture of gas films. The coalescence of two antibubbles, which shows a similar merging process of soap bubbles, also undergo the rupture and formation of gas films. The rupture of gas film of antibubble caused by aging and impact is also discussed.

Visual Observations of Chamber Volume Effect on Ebullience From Submerged Orifice Plates

2016 ◽  
Author(s):  
Sanjivan Manoharan ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
Bubble Growth ◽  
High Speed ◽  
Capillary Tube ◽  
Volume Effect ◽  
Orifice Plate ◽  
Orifice Diameter ◽  
Chamber Volume ◽  
Acrylic Glass ◽  
Liquid Pools

Effect of chamber volume upstream of the orifice on ebullience from orifice plates is studied experimentally in this paper. Bubble growth from orifice plates submerged in liquid pools is captured using high speed videography. The orifice plate substrate is acrylic glass and 11 different orifice diameters (diameter range: 0.610< D0< 2.261mm) are utilized. In addition to water, ethanol-water binary mixture with surface tension of 54 mN/m is used to examine the interplay between surface tension and chamber volume effects on bubble characteristics. For an acrylic glass orifice plate with a fixed chamber volume, above a certain transition orifice diameter, the bubbles from the orifice plate are of the same size and shape as those from a capillary tube orifice. However, below this diameter, the bubbles from the orifice plate show significantly different characteristics due to the chamber volume effect. The bubbles are more spherical in shape with the apex being sharper and more pointed. The bubbles also tend to sit closer to the plate due to their abnormally large size while the growth times are much shorter. These differences are highlighted by comparing photographs of bubble growth with and without the chamber volume effect. Additionally, for the medium chamber region, an empirical correlation was proposed to predict bubble departure diameters to within ±15 %. For a fixed chamber volume, variation in surface tension showed no change in the transition orifice diameter.

Deposition Process of Droplets Impacting on a Horizontal Surface

2011 ◽  
Vol 354-355 ◽  
pp. 579-584 ◽  
Author(s):  
Jing Yin Li ◽  
Qiang Han ◽  
Yan Jie Zhao ◽  
Xiao Fang Yuan
Keyword(s):  
Impact Velocity ◽  
High Speed ◽  
Droplet Impact ◽  
Numerical Results ◽  
Horizontal Surface ◽  
Experimental Investigations ◽  
Impact Process ◽  
Vof Model ◽  
Spread Factor ◽  
The Impact

The results of the experimental investigations and numerical simulations of droplet impact on a stationary horizontal surface are presented. The impact process of a droplet with high impact energy on a horizontal surface was photographed by a high-speed CCD. In addition, two-dimensional numerical simulation of the impact process was also performed using the VOF model. Comparison between the experimental and numerical results shows that the chosen computational model is suitable to simulate such impact processes. Furthermore, the effect of the droplet impact velocity and diameter on the impact process was studied in detailed. The numerical results show that the variation in droplet impact velocity has a significant effect on the maximum spread factor and spread speed, whereas, the variation in droplet diameter considerably influences the maximum spread factor and the oscillation of the drop in the receding phase.

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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