scholarly journals A new bubble dynamics model to study bubble growth, deformation, and coalescence

2014 ◽  
Vol 119 (1) ◽  
pp. 216-239 ◽  
Author(s):  
C. Huber ◽  
Y. Su ◽  
C. T. Nguyen ◽  
A. Parmigiani ◽  
H. M. Gonnermann ◽  
...  
Keyword(s):  
Bubble Growth ◽  
Bubble Dynamics ◽  
Dynamics Model

Decompression Sickness Treatment Using a Pressure Suit After Loss of Spacecraft Atmosphere

2020 ◽  
Vol 91 (7) ◽  
pp. 571-577
Author(s):  
Michael R. Greene ◽  
Shane E. Jacobs
Keyword(s):  
Symptom Onset ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Decompression Sickness ◽  
Treatment Model ◽  
Dynamics Model ◽  
Symptom Resolution ◽  
Entry Pressure ◽  
Operational Concept ◽  
Over Time

BACKGROUND: Loss of spacecraft atmosphere (LOA) during Earth-Moon transit may require up to 144 h of pressure suit operations. This work investigates the feasibility of DCS treatment in this paradigm and discusses the operational and engineering implications.METHODS: Three scenarios of LOA-induced DCS were considered: a permanent LOA secondary to a 0.25-in (0.64 cm) hole (unrecoverable cabin leak), a transient LOA, and a permanent LOA with early suit over-pressurization (beyond suit specification). Each was simulated in the context of the current Orion spacecraft operational concept with regards to atmosphere and anticipated cabin depress profile. Probability of DCS symptom resolution (P(SR)) was estimated using the previously derived Hypobaric DCS Treatment Model, with ΔP calculated from a Three Region Well-Stirred Tissue (3RWT) bubble dynamics model. Analysis was conducted and analogies drawn from experiences with the development and testing of the Orion Crew Survival System (OCSS).RESULTS: Maintaining 8 psia at 100% Fio2 following LOA resulted in an eventual halt and regression of bubble growth with a P(SR) of 87% (at 8 h, time to symptom onset (Ts) = 105 min, with ambulation). If cabin atmosphere was not restored and psia dropped to 4.3, bubble growth returned, but again eventually slowed and regressed over time (P(SR) = 75% at 21 h). If the leak is repaired within the 8-h period, 8 psid (psia = 22.7) resulted in P(SR) of greater than 95%. Similarly, if the suit was over-pressurized (12 psid/psia) within 3 h after LOA, P(SR) exceeded 95%.DISCUSSION: A launch/entry pressure suit represents a contingency option for DCS management in the event of LOA.Greene MR, Jacobs SE. Decompression sickness treatment using a pressure suit after loss of spacecraft atmosphere. Aerosp Med Hum Perform. 2020; 91(7):571–577.

Study on the Bubble Dynamics and the Exciting Force in a Bended Pipe Based on BEM

2016 ◽  
Author(s):  
Y. L. Liu ◽  
Z. L. Tian
Keyword(s):  
Numerical Model ◽  
Potential Theory ◽  
Bubble Dynamics ◽  
Flow Speed ◽  
Exciting Force ◽  
Incoming Flow ◽  
Bubble Motion ◽  
Dynamics Model ◽  
Pipe Surface ◽  
Direction Change

Nonlinear bubble dynamics in a pipeline and its exciting force are investigated by a numerical model based on BEM. The bubble motion is one of the main causes that the pipeline vibrates and generates noise in modern ships. The numerical bubble dynamics model is established under the incompressible potential theory. Bubble motion with different incoming flow in a bended pipe is simulated. We found that the bubble develops jet when it passes by the bend, and adjoin to the pipe surface in the side of the fillet center. The pulsation and the direction change of the bubble apply an exciting force on the pipe which has a positive correlation with the incoming flow speed and may lead vibration and noise.

Numerical Study of Bubble Growth on a Micro-Finned Surface

2011 ◽  
Author(s):  
Woorim Lee ◽  
Gihun Son
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Removal Rate ◽  
Bubble Formation ◽  
Experimental Studies ◽  
Nucleate Boiling ◽  
Finned Surface ◽  
Fin Spacing

Bubble growth on a micro-finned surface, which can be used in enhancing boiling heat transfer, is numerically investigated by solving the conservation equations of mass, momentum, and energy. The bubble deformation or the liquid-vapor interface is determined by the sharp-interface level-set method, which is modified to include the effect of phase change and to treat the contact angle and the evaporative heat flux from the liquid microlayer on an immersed solid surface of a microfin. The numerical method is applied to clarify bubble growth and heat transfer characteristics on a surface including fin and cavity during nucleate boiling which have not been provided from the previous experimental studies. The effects of single fin, fin-cavity distance, and fin-fin spacing on the bubble dynamics are investigated. The micro-fin is found to affect the activation of cavity. The fin-cavity configuration is found to determine the bubble formation in a cavity. The vapor removal rate is also observed to significantly depend on the fin-fin spacing.

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.

Simulation of bubble growth and collapse in linear and pom-pom polymers

e-Polymers ◽  
2002 ◽  
Vol 2 (1) ◽  
Author(s):  
Uday S. Agarwal
Keyword(s):  
Bubble Growth ◽  
Bubble Dynamics ◽  
Polymer Melt ◽  
Integral Form ◽  
Polymer Chains ◽  
Bubble Collapse ◽  
Flow Strength ◽  
Branch Lengths ◽  
Programming Effort ◽  
Viscoelastic Liquids

AbstractExisting approaches to simulate the bubble growth/collapse in viscoelastic liquids use the integral form of a constitutive equation, that can additionally be analytically integrated over the radial domain. Here we represent the process by a system of simultaneous partial differential equations, with fixed and finite boundaries. This enables a direct computer implementation with commercially available software, with little additional programming effort. The involved co-ordinate transformation preferably does not correspond to the material co-ordinates. The surrounding liquid can be simulated as being a finite film or of infinite extent, with simply a change in one computational parameter. We simulate hydrodynamically induced bubble dynamics in viscolelastic liquids, and estimate the flow strength (elongational strain rate) and its possible role in flow induced scission of polymer chains in liquids experiencing bubble collapse. Calculations are also performed to evaluate the influence of backbone and branch lengths when the surrounding fluid is a branched polymer melt, using the pom-pom model to describe the rheological behavior.

Experimental Study of Bubble Dynamics on a Micro Heater Induced by Pulse Heating

2004 ◽  
Vol 126 (2) ◽  
pp. 259-271 ◽  
Author(s):  
Y. Hong ◽  
N. Ashgriz ◽  
J. Andrews
Keyword(s):  
Experimental Study ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Pulse Heating ◽  
Deionized Water ◽  
Nucleation Theory ◽  
Electric Pulses ◽  
Pressure Profiles ◽  
Rapid Formation ◽  
Resistive Heater

An experimental investigation of the rapid formation and collapse of bubbles formed on a micro heater (25×80 μm2) is presented. Short electric pulses in the range of 1 μs to 4 μs are applied to the resistive heater, which is immersed in deionized water and generates a heat flux of more than 750 MW/m2. A stroboscopic technique with a time resolution of 30 ns and spatial resolution of 2 μm was used to capture the dynamics of the bubble growth and collapse. From the nucleation theory, the nucleation temperatures are close to the kinetic limit of superheat and weakly depends on the heating rate. The velocity, acceleration, and the pressure profiles after the vapor sheet formation are presented.

Scaling of Tip Vortex Cavitation Inception Noise With a Bubble Dynamics Model Accounting for Nucleus Size Distribution

2003 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Georges L. Chahine
Keyword(s):  
Size Distribution ◽  
Vortex Flow ◽  
Bubble Dynamics ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Nucleus Size ◽  
Scaling Effects ◽  
Dynamics Model ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception

A Surface-Averaged Pressure (SAP) spherical bubble dynamics model accounting for a statistical nuclei size distribution was used to model the acoustic signals generated by cavitating bubbles near inception in a tip vortex flow. The flow field generated by finite-span elliptic hydrofoils is obtained by Reynolds-Averaged Navier-Stokes computations. An “acoustic” criterion which defines the cavitation inception by counting the number of acoustical signal peaks that exceed a certain level per unit time was applied to deduce the cavitation inception number for different scales. It was found that the larger scale results in more cavitation inception events per unite time because more nuclei are excited by the tip vortex at the larger scale. The nuclei size was seen to have an important effect on cavitation inception number with scaling effects due to nuclei increasing as nuclei sizes decreases.

scholarly journals Gas bubble dynamics model for shallow volcanic tremor at Stromboli

1999 ◽  
Vol 104 (B5) ◽  
pp. 10639-10654 ◽  
Author(s):  
Maurizio Ripepe ◽  
Evgenii Gordeev
Keyword(s):  
Bubble Dynamics ◽  
Volcanic Tremor ◽  
Gas Bubble ◽  
Dynamics Model

Characteristics of Nucleation and Bubble Growth During Microscale Boiling

2005 ◽  
Author(s):  
Yong Tian ◽  
Jiang-Tao Liu ◽  
Xiao-Feng Peng
Keyword(s):  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Ccd Camera ◽  
Initial Position ◽  
Length Scale ◽  
Formation Theory ◽  
Nucleus Formation ◽  
Microlayer Evaporation ◽  
Parallel Microchannels

In this paper, both nucleus formation and bubble growth during boiling in microchannels were investigated. A series of visualized experiments were conducted to observe the boiling nucleation and bubble dynamics restricted within parallel microchannels on a silicon wafer. The channels were rectangular and had selected length scale ranging from 50 to 100 microns. A high-speed CCD camera was employed together with a microscope to dynamically record the boiling images. The rates of bubble growth were measured in the channels. The phase change nucleus formation theory was used to determine the initial position of the bubble. The bubble growth rate was described by two ordinary differential equations deduced from the microlayer evaporation theory. The calculation and experimental results were reasonably coincided.

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