Single Bubble Dynamics on a Hydrophobic Surface

2007 ◽  
Author(s):  
Youngsuk Nam ◽  
Gopinath Warrier ◽  
Jinfeng Wu ◽  
Y. Sungtaek Ju
Keyword(s):  
Silicon Substrate ◽  
Bubble Dynamics ◽  
Growth Period ◽  
Hydrophobic Surface ◽  
Nucleation Site ◽  
Bubble Surface ◽  
Bubble Nucleation ◽  
Root Mean Square Roughness ◽  
Static Contact ◽  
Artificial Cavity

The growth and departure of single bubbles on two surfaces with very different wettability is studied using highspeed video microscopy. An artificial cavity of approximately 10μm diameter is microfabricated on a bare and a Teflon-coated silicon substrate to serve as a nucleation site. The static contact angle of water is approximately 40° on the bare silicon substrate and approximately 120° on the Teflon-coated substrate. The bubble departure diameter is observed to be almost three times larger and the growth period almost 60 times longer for the hydrophobic surface than for the hydrophilic surface. The waiting period is practically zero for the hydrophobic surface because a small residual bubble nucleus remains on the cavity from the previous ebullition cycle. Bubble nucleation occurs on nominally smooth hydrophobic regions with root mean square roughness below 4 nm even at superheat as small as 4 °C. Liquid subcooling significantly affects bubble growth on the hydrophobic surface due to the increased bubble surface area.

Experimental and Numerical Study of Single Bubble Dynamics on a Hydrophobic Surface

2007 ◽  
Author(s):  
Youngsuk Nam ◽  
Gopinath Warrier ◽  
Jinfeng Wu ◽  
Y. Sungtaek Ju
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Growth Period ◽  
Hydrophobic Surface ◽  
Bubble Surface ◽  
Bubble Nucleation ◽  
Root Mean Square Roughness ◽  
Energy Harvesters ◽  
Enhanced Boiling

The growth and departure of single bubbles on two surfaces with very different wettability is studied using high-speed video microscopy and numerical simulation. Isolated artificial cavities of approximately 10μm diameter are microfabricated on a bare and a Teflon-coated silicon substrate to serve as nucleation sites. The bubble departure diameter is observed to be almost three times larger and the growth period almost 60 times longer for the hydrophobic surface than for the hydrophilic surface. The waiting period is practically zero for the hydrophobic surface because a small residual bubble nucleus is left behind on the cavity from the previous ebullition cycle. The experimental results are consistent with our numerical simulations. Bubble nucleation occurs on nominally smooth hydrophobic regions with root mean square roughness (Rq) less than 1 nm even at superheat as small as 3 °C. Liquid subcooling significantly affects bubble growth on the hydrophobic surface due to increased bubble surface area. Fundamental understanding of bubble dynamics on heated hydrophobic surfaces will help to develop chemically patterned surfaces with enhanced boiling heat transfer and novel phase-change based micro-actuators and energy harvesters.

Experimental and Numerical Study of Single Bubble Dynamics on a Hydrophobic Surface

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Youngsuk Nam ◽  
Jinfeng Wu ◽  
Gopinath Warrier ◽  
Y. Sungtaek Ju
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Growth Period ◽  
Hydrophobic Surface ◽  
Bubble Surface ◽  
Bubble Nucleation ◽  
Root Mean Square Roughness ◽  
Energy Harvesters ◽  
Enhanced Boiling

The growth and departure of single bubbles on two smooth surfaces with very different wettabilities are studied using high-speed video microscopy and numerical simulations. Isolated artificial cavities of approximately 10 μm diameter are microfabricated on both a bare and a Teflon-coated silicon substrate to serve as nucleation sites. The bubble departure diameter is observed to be almost 3 times larger and the growth period almost 60 times longer for the hydrophobic surface than for the hydrophilic surface. The waiting period is practically zero for the hydrophobic surface because a small residual bubble nucleus is left behind on the cavity from a previous ebullition cycle. The experimental results are consistent with our numerical simulation results. Bubble nucleation occurs on nominally smooth hydrophobic regions with root mean square roughness (Rq) less than 1 nm even at superheat as small as 3°C. Liquid subcooling significantly affects bubble growth on the hydrophobic surface due to increased bubble surface area. Fundamental understanding of bubble dynamics on heated hydrophobic surfaces will facilitate the development of chemically patterned surfaces with enhanced boiling heat transfer performance and novel phase-change based micro-actuators and energy harvesters.

Review on Bubble Dynamics in Microchannel Heat Sink

2019 ◽  
Author(s):  
Sambhaji T. Kadam ◽  
Ibrahim Hassan ◽  
Ritunesh Kumar ◽  
Aziz Rahman
Keyword(s):  
Bubble Growth ◽  
Bubble Dynamics ◽  
Growth Models ◽  
Flow Boiling ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Detailed Knowledge ◽  
Diffusion Controlled

Abstract Inception of the boiling, in pool or flow boiling, is the formation of the vapour bubble at active nucleation site. The bubble dynamics plays an important role in the boiling process. It is critical as it unfolds many facets especially when channel size is reduced to submicron. The detailed knowledge of the bubble dynamics is helpful in establishing the thermal and hydraulic flow behaviour in microchannel. In this paper, the bubble dynamics which include bubble nucleation at nucleation site, its growth, departure and motion along the flow in a microchannel are discussed in details. Different models are developed for the critical cavity radius are compiled and observed that they show large variation when compare. The bubble growth models are compiled and concluded that a development of more generalized bubble growth model is necessary to account for the inertia controlled and thermal diffusion controlled regions. The bubble at the nucleation site in a microchannel grows under the influence of various forces such as surface tension, inertia, shear, gravitational and evaporation momentum. Parametric variations of these forces are critically studied and reckoned that the slope of these forces seems to be reduced beyond 500 μm. Eventually, possible impact of the various factors such as operating conditions, geometrical parameters, and thermophysical properties of fluid on bubble dynamics in microchannel has been reported.

Experimental Study of Effect of Nucleation Site Size on Bubble Dynamics during Nucleate Pool Boiling Heat Transfer

2014 ◽  
Vol 592-594 ◽  
pp. 1596-1600 ◽  
Author(s):  
Abdul Najim ◽  
Anil R. Aacharya
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Growth Period ◽  
Nucleation Site ◽  
Hypodermic Needle ◽  
Nucleate Pool Boiling ◽  
Pool Boiling Heat Transfer

In this paper, effect of nucleation site size on bubble dynamics during nucleate pool boiling heat transfer in saturated water is studied experimentally. Single bubble was generated using right angle tip of a hypodermic needle as a nucleation site. The hypodermic needles were used of inner diameters 0.413mm, 0.514mm, and 0.603 mm with a constant depth of 25mm. The bubble dynamics was studied using SONY Cyber-shot DSC-H100 camera operating at 30 frames per second at atmospheric pressure and at a wall superheat of 5K. The results show that, bubble diameter, bubble height and bubble volume increases with increase in diameter of nucleation site. The bubble growth period is found to be dependent on nucleation site size, and it decreases with increase in diameter of nucleation site. This happens because as volume of vapor bubble increases, buoyancy force starts dominates the capillary force and bubble detaches earlier. Effect of nucleation site size on bubble departure diameter and bubble release frequency is also discussed.

Bubble Growth at Nucleation Cavity in Microchannels

2013 ◽  
Author(s):  
Sambhaji T. Kadam ◽  
Ritunesh Kumar ◽  
Kuldeep Baghel
Keyword(s):  
Vapor Phase ◽  
Waiting Time ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Two Phase ◽  
Proposed Model ◽  
Gravity Effects

Bubble dynamics i.e. bubble nucleation, growth and departure plays an important role in heat transfer and pressure drop characteristics during two phase flow of microchannels. A simplified mathematical model has been developed to predict the bubble growth rate in microchannels at nucleation cavity after its inception. It is assumed that heat supplied at nucleation site is divided between liquid phase and vapor phase as per instantaneous void fraction value. The energy consumed by vapor phase is utilized in overcoming evaporation, surface tension, inertia, shear and gravity effects. Proposed model shows good agreement (∼14 % error) with available experimental work. In addition, the physical phenomena of the bubble waiting time for flow boiling is also addressed utilizing proposed model. The waiting time predicted by the model is close to that obtained from experimental data.

scholarly journals Phase transitions from the fifth dimension

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Kaustubh Agashe ◽  
Peizhi Du ◽  
Majid Ekhterachian ◽  
Soubhik Kumar ◽  
Raman Sundrum
Keyword(s):  
Bubble Dynamics ◽  
Effective Field ◽  
Bubble Nucleation ◽  
Thin Wall ◽  
Black Brane ◽  
Composite Higgs ◽  
Fifth Dimension ◽  
Two Phases ◽  
Holographic Description ◽  
The Impact

Abstract We study the cosmological transition of 5D warped compactifications, from the high-temperature black-brane phase to the low-temperature Randall-Sundrum I phase. The transition proceeds via percolation of bubbles of IR-brane nucleating from the black-brane horizon. The violent bubble dynamics can be a powerful source of observable stochastic gravitational waves. While bubble nucleation is non-perturbative in 5D gravity, it is amenable to semiclassical treatment in terms of a “bounce” configuration interpolating between the two phases. We demonstrate how such a bounce configuration can be smooth enough to maintain 5D effective field theory control, and how a simple ansatz for it places a rigorous lower-bound on the transition rate in the thin-wall regime, and gives plausible estimates more generally. When applied to the Hierarchy Problem, the minimal Goldberger-Wise stabilization of the warped throat leads to a slow transition with significant supercooling. We demonstrate that a simple generalization of the Goldberger-Wise potential modifies the IR-brane dynamics so that the transition completes more promptly. Supercooling determines the dilution of any (dark) matter abundances generated before the transition, potentially at odds with data, while the prompter transition resolves such tensions. We discuss the impact of the different possibilities on the strength of the gravitational wave signals. Via AdS/CFT duality the warped transition gives a theoretically tractable holographic description of the 4D Composite Higgs (de)confinement transition. Our generalization of the Goldberger-Wise mechanism is dual to, and concretely models, our earlier proposal in which the composite dynamics is governed by separate UV and IR RG fixed points. The smooth 5D bounce configuration we introduce complements the 4D dilaton/radion dominance derivation presented in our earlier work.

Formulation of a Mathematical Process Model for the Foaming of a Mesophase Carbon Precursor

1992 ◽  
Vol 270 ◽  
Author(s):  
S. S. Sandhu ◽  
J. W. Hager
Keyword(s):  
Process Model ◽  
Analytical Description ◽  
Nucleation And Growth ◽  
Bubble Surface ◽  
Bubble Nucleation ◽  
Mesophase Pitch ◽  
Experimental Production ◽  
Mathematical Equations ◽  
Experimental Effort ◽  
Mathematical Process

ABSTRACTMathematical equations have been formulated to guide an experimental effort to produce an open-celled mesophase pitch foam. The formulation provides an analytical description of homogeneous bubble nucleation and growth, diffusion of the blowing gas through the liquid to the bubble surface, and the average material thickness between bubbles. Implications of the formulation for the experimental production of mesophase pitch foam are discussed.

Intramicroparticle nitrogen dioxide is a bubble nucleation site leading to decompression-induced neutrophil activation and vascular injury

2013 ◽  
Vol 114 (5) ◽  
pp. 550-558 ◽  
Author(s):  
Stephen R. Thom ◽  
Ming Yang ◽  
Veena M. Bhopale ◽  
Tatyana N. Milovanova ◽  
Marina Bogush ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Ex Vivo ◽  
Ambient Pressure ◽  
Annexin V ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Neutrophil Activation ◽  
Inert Gases ◽  
Wild Type ◽  
Inos Inhibitor

Inert gases diffuse into tissues in proportion to ambient pressure, and when pressure is reduced, gas efflux forms bubbles due to the presence of gas cavitation nuclei that are predicted based on theory but have never been characterized. Decompression stress triggers elevations in number and diameter of circulating annexin V-coated microparticles (MPs) derived from vascular cells. Here we show that ∼10% MPs from wild-type (WT) but not inflammatory nitric oxide synthase-2 (iNOS) knockout (KO) mice increase in size when exposed to elevated air pressure ex vivo. This response is abrogated by a preceding exposure to hydrostatic pressure, demonstrating the presence of a preformed gas phase. These MPs have lower density than most particles, 10-fold enrichment in iNOS, and generate commensurately more reactive nitrogen species (RNS). Surprisingly, RNS only slowly diffuse from within MPs unless particles are subjected to osmotic stress or membrane cholesterol is removed. WT mice treated with iNOS inhibitor and KO mice exhibit less decompression-induced neutrophil activation and vascular leak. Contrary to injecting naïve mice with MPs from wild-type decompressed mice, injecting KO MPs triggers fewer proinflammatory events. We conclude that nitrogen dioxide is a nascent gas nucleation site synthesized in some MPs and is responsible for initiating postdecompression inflammatory injuries.

scholarly journals Bubble Dynamics in Soft and Biological Matter

2019 ◽  
Vol 51 (1) ◽  
pp. 331-355 ◽  
Author(s):  
Benjamin Dollet ◽  
Philippe Marmottant ◽  
Valeria Garbin
Keyword(s):  
Viscoelastic Medium ◽  
Bubble Dynamics ◽  
Nonlinear Behavior ◽  
Bubble Surface ◽  
Solid Particles ◽  
Advanced Materials ◽  
Viscoelastic Layer ◽  
Future Research ◽  
Oscillatory Dynamics ◽  
Biological Matter

Bubbles are present in a large variety of emerging applications, from advanced materials to biology and medicine, as either laser-generated or acoustically driven bubbles. In these applications, the bubbles undergo oscillatory dynamics and collapse inside—or near—soft and biological materials. The presence of a soft, viscoelastic medium strongly affects the bubble dynamics, both its linear resonance properties and its nonlinear behavior. Surfactant molecules or solid particles adsorbed on a bubble surface can also modify the bubble dynamics through the rheological properties of the interfacial layer. Furthermore, the interaction of bubbles with biological cells and tissues is highly dependent on the mechanical properties of these soft deformable media. This review covers recent developments in bubble dynamics in soft and biological matter for different confinement conditions: bubbles in a viscoelastic medium, coated by a viscoelastic layer, or in the vicinity of soft confinement or objects. The review surveys current work in the field and illustrates open questions for future research.

Experimental Study of Bubble Dynamics and Concentration Variation in the Presence of Boron in the Liquid

2002 ◽  
Author(s):  
W. Jia ◽  
V. K. Dhir
Keyword(s):  
Bubble Dynamics ◽  
Concentration Field ◽  
Nucleation Site ◽  
Single Bubble ◽  
Boron Compounds ◽  
Measured Concentration ◽  
Neutron Absorber ◽  
Concentration Variation ◽  
Water Reactors ◽  
Miniature Sensor

Accumulation of neutron absorber (boron or boron compounds) within the porous crud layer on the fuel rods in the cores of pressured water reactors (PWR) results in the so-called axial offset anomaly (AOA). There is practically little information on the gradients of neutron absorber concentration near a nucleation site on the cladding surface during the growth of a bubble. The objective of the present work is to study bubble dynamics and associated concentration field of aqueous boron. As a first step in solving the complete problem, dynamics of single bubble was studied under pool boiling conditions. Distilled water and an aqueous solution containing 3,000ppm by weight of boric acid were used as test liquids. Single bubble was generated at a micro-fabricated cavity on a polished silicon wafer. It was found that the growth and departure processes of single bubbles are similar for both the test liquids. A miniature sensor for measurement of concentration was developed and calibrated. Concentration variation near the liquid-vapor interface was detected successfully. The measured concentration variations at different radial locations from the center of cavity have the same trend as given by the numerical simulations but the magnitude is much smaller.

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