A General Approach for Rectified Mass Diffusion of Gas Bubbles in Liquids Under Acoustic Excitation

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Yuning Zhang ◽  
Shengcai Li
Keyword(s):  
Biomedical Engineering ◽  
Thermal Effects ◽  
Gas Bubbles ◽  
Mass Diffusion ◽  
Present Approach ◽  
Acoustic Excitation ◽  
Gas Bubble ◽  
Bubble Motion ◽  
Acoustic Dissipation ◽  
Bubble Oscillations

Rectified mass diffusion serves as an important mechanism for dissolution or growth of gas bubbles under acoustic excitation with many applications in acoustical, chemical and biomedical engineering. In this paper, a general approach for predicting rectified mass diffusion phenomenon is proposed based on the equation of bubble motion with liquid compressibility. Nonuniform pressure inside gas bubbles is considered in the approach through employing a well-established framework relating with thermal effects during gas bubble oscillations. Energy dissipation mechanisms (i.e., viscous, thermal, and acoustic dissipation) and surface tension are also included in the approach. Comparing with previous analytical investigations, present approach mainly improves the predictions of rectified mass diffusion in the regions far above resonance and regions with frequencies megahertz and above. Mechanisms for the improvements are shown and discussed together with valid regions and limitations of present approach.

Gas bubble induced scalings in geothermal systems

2021 ◽  
Author(s):  
Lilly Zacherl ◽  
Thomas Baumann
Keyword(s):  
Ph Value ◽  
Saturation Index ◽  
Gas Bubbles ◽  
Gas Bubble ◽  
Geothermal Systems ◽  
Injection Wells ◽  
Term Operation ◽  
Maintenance Schedule ◽  
Local Experience ◽  
Maintenance Schedules

<p>Scalings in geothermal systems are affecting the efficiency and safety of geothermal systems. An operate-until-fail maintenance scheme might seem appropriate for subsurface installations where the replacement of pumps and production pipes is costly and regular maintenance comprises a complete overhaul of the installations. The situation is different for surface level installations and injection wells. Here, monitoring of the thickness of precipitates is the key to optimized maintenance schedules and long-term operation.</p><p>A questionnaire revealed that operators of geothermal facilities start with a standardized maintenance schedule which is adjusted based on local experience. Sensor networks, numerical modelling and predictive maintenance are not yet applied. In this project we are aiming to close this gap with the development of a non-invasive sensor system coupled to innovative data acquisition and evaluation and an expert system to quantitatively predict the development of precipitations in geothermal systems and open cooling towers.</p><p>Previous investigations of scalings in the lower part of production pipes of a geothermal facility suggest that the disruption of the carbonate equilibrium is triggered by the formation of gas bubbles in the pump and subsequent stripping of CO<sub>2</sub>. Although small in it's overall effect on pH-value and saturation index, significant amounts of precipitates are forming at high volumetric flow rates. To assess the kinetics of gas bubble induced precipitations laboratory experiments were run. The experiment addresses precipitations at surfaces and at the gas bubbles themselves.</p>

Nuclei and Cavitation

1970 ◽  
Vol 92 (4) ◽  
pp. 681-688 ◽  
Author(s):  
J. William Holl
Keyword(s):  
Bubble Growth ◽  
Scale Effects ◽  
Gas Bubbles ◽  
Gas Content ◽  
Gas Bubble ◽  
Cavitation Nuclei ◽  
The Stability

This paper is a review of existing knowledge on cavitation nuclei. The lack of significant tensions in ordinary liquids is due to so-called weak spots or cavitation nuclei. The various forms which have been proposed for nuclei are gas bubbles, gas in a crevice, gas bubble with organic skin, and a hydrophobic solid. The stability argument leading to the postulation of the Harvey model is reviewed. Aspects of bubble growth are considered and it is shown that bubbles having different initial sizes will undergo vaporous cavitation at different liquid tensions. The three modes of growth, namely vaporous, pseudo, and gaseous are presented and implications concerning the interpretation of data are considered. The question of the source of nuclei and implications concerning scale effects are made. The measurement of nuclei is considered together with experiments on the effect of gas content on incipient cavitation.

Behavior of Inert Gas Bubbles in Forced Convective Liquid Metal Circuits

1976 ◽  
Vol 98 (1) ◽  
pp. 5-11 ◽  
Author(s):  
W. J. Minkowycz ◽  
D. M. France ◽  
R. M. Singer
Keyword(s):  
Liquid Metal ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Gas Bubbles ◽  
Inert Gas ◽  
Liquid Sodium ◽  
Gas Bubble ◽  
Flowing Liquid ◽  
Argon Gas ◽  
The Core

Conservation equations are derived for the motion of a small inert gas bubble in a large flowing liquid-gas solution subjected to large thermal gradients. Terms which are of the second order of magnitude under less severe and steady-state conditions are retained, thus resulting in an expanded form of the Rayleigh equation. The bubble dynamics is a function of opposing mechanisms tending to increase or decrease bubble volume while being transported with the solution. Diffusion of inert gas between the bubble and the solution is one of the most important of these mechanisms included in the analysis. The analytical model is applied to an argon gas bubble flowing in a weak solution of argon gas in liquid sodium. Calculations are performed for these fluids under conditions typical of normal and abnormal operation of a liquid metal fast breeder reactor (LMFBR) core and the resulting bubble radius, internal gas pressure, and mass of inert gas are presented in each case. An important result obtained indicates that inert gas bubbles reaching the core inlet of an LMFBR will always grow as they traverse the core under normal and extreme abnormal conditions and that the rate of growth is quite small in all cases.

Rectified diffusion during nonlinear gas bubble oscillations

1991 ◽  
Vol 89 (4B) ◽  
pp. 1863-1863
Author(s):  
Vinod Kamath ◽  
Andrea Prosperetti
Keyword(s):  
Gas Bubble ◽  
Bubble Oscillations

scholarly journals Chaotic gas bubble oscillations in a viscoelastic fluid

2008 ◽  
Vol 336 (5) ◽  
pp. 411-416 ◽  
Author(s):  
Javier Jiménez-Fernández
Keyword(s):  
Viscoelastic Fluid ◽  
Gas Bubble ◽  
Bubble Oscillations

A Generalized Equation for Scattering Cross Section of Spherical Gas Bubbles Oscillating in Liquids Under Acoustic Excitation

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Yuning Zhang
Keyword(s):  
Cross Section ◽  
Acoustic Waves ◽  
Ambient Pressure ◽  
Gas Bubbles ◽  
Resonance Region ◽  
Generalized Equation ◽  
Scattering Cross Section ◽  
Acoustic Excitation ◽  
Spherical Waves ◽  
Scattering Cross

When irradiated by acoustic waves, gas bubbles can generate divergent spherical waves, which are frequently used to detect the sizes and number density of the gas bubbles. In this paper, a generalized equation for scattering cross section of spherical gas bubbles oscillating in liquids under acoustic excitation is proposed. Comparing with formulas in the literature, this generalized equation can improve the predictions of acoustical scattering cross section in the near-resonance region with high ambient pressure and above-resonance region.

Sign in / Sign up

Export Citation Format

Share Document