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.

The Influence of Velocity and Scale on Cavitation Inception where Wall-Generated Gas Bubbles are the Sole Source of Cavitation Nuclei

1975 ◽  
Vol 17 (2) ◽  
pp. 45-51
Author(s):  
M. R. Baum
Keyword(s):  
Bubble Growth ◽  
Flow System ◽  
Scale Effects ◽  
Gas Bubbles ◽  
Sole Source ◽  
Gas Bubble ◽  
Cavitation Inception ◽  
Boundary Wall ◽  
Cavitation Nuclei ◽  
System Properties

It is established, using recently derived expressions relating the flow system properties to the size at which a gas bubble grown at a boundary wall will become detached, that the commonly observed variation in cavitation inception pressure with velocity in a given system can be simply attributed to variations in the size of bubble detached. However, it is concluded, from a comparison of predicted and experimental variations of inception pressure with scale of the system, that when considering scale effects the pressure necessary to promote gas-bubble growth must also be taken into account.

Observation and Quantification of Gas Bubble Formation on a Mechanical Heart Valve

2000 ◽  
Vol 122 (4) ◽  
pp. 304-309 ◽  
Author(s):  
Hsin-Yi Lin ◽  
Brian A. Bianccucci ◽  
Steven Deutsch ◽  
Arnold A. Fontaine ◽  
J. M. Tarbell
Keyword(s):  
High Speed ◽  
Heart Valves ◽  
Bubble Formation ◽  
Mechanical Heart Valve ◽  
Gas Bubbles ◽  
Co2 Concentration ◽  
Video Camera ◽  
Gas Content ◽  
Gas Bubble ◽  
Cavitation Intensity

Clinical studies using transcranial Doppler ultrasonography in patients with mechanical heart valves (MHV) have detected gaseous emboli. The relationship of gaseous emboli release and cavitation on MHV has been a subject of debate in the literature. To study the influence of cavitation and gas content on the formation and growth of stable gas bubbles, a mock circulatory loop, which employed a Medtronic-Hall pyrolytic carbon disk valve in the mitral position, was used. A high-speed video camera allowed observation of cavitation and gas bubble release on the inflow valve surfaces as a function of cavitation intensity and carbon dioxide CO2 concentration, while an ultrasonic monitoring system scanned the aortic outflow tract to quantify gas bubble production by calculating the gray scale levels of the images. In the absence of cavitation, no stable gas bubbles were formed. When gas bubbles were formed, they were first seen a few milliseconds after and in the vicinity of cavitation collapse. The volume of the gas bubbles detected in the aortic track increased with both increased CO2 and increased cavitation intensity. No correlation was observed between O2 concentration and bubble volume. We conclude that cavitation is an essential precursor to stable gas bubble formation, and CO2, the most soluble blood gas, is the major component of stable gas bubbles. [S0148-0731(00)00204-1]

On Bounds for the Threshold Pressure Initiating Bubble Growth

1973 ◽  
Vol 95 (1) ◽  
pp. 98-102 ◽  
Author(s):  
Bror Persson
Keyword(s):  
Bubble Growth ◽  
Incompressible Liquid ◽  
Pressure Pulse ◽  
Gas Content ◽  
Upper And Lower Bounds ◽  
Threshold Pressure ◽  
Gas Bubble ◽  
Viscous Incompressible Liquid ◽  
Vanishing Viscosity ◽  
Onset Of Cavitation

Conditions are investigated for the onset of the growth of a spherical gas bubble in a viscous, incompressible liquid. The bubble is assumed to be exposed to a step pressure pulse of infinite duration. It is found that upper and lower bounds for the threshold pressure exist and occur for infinite and vanishing viscosity, respectively. The analysis indicates that the effects of inertia, viscosity, and thermodynamic state of the gas have little influence on the threshold pressure, while the effect of the gas content in the bubble is considerable. The problem considered is to some extent related to the onset of cavitation.

Understanding gas bubble trauma in an era of hydropower expansion: how do fish compensate at depth?

2020 ◽  
Vol 77 (3) ◽  
pp. 556-563 ◽  
Author(s):  
Naomi K. Pleizier ◽  
Charlotte Nelson ◽  
Steven J. Cooke ◽  
Colin J. Brauner
Keyword(s):  
Bubble Growth ◽  
Gas Bubble ◽  
Hydroelectric Dams ◽  
Dissolved Gas ◽  
Empirical Relationships ◽  
Lethal Effects ◽  
Exposed Fish ◽  
Total Dissolved Gas ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
The Relationship

Hydrostatic pressure is known to protect fish from damage by total dissolved gas (TDG) supersaturation, but empirical relationships are lacking. In this study we demonstrate the relationship between depth, TDG, and gas bubble trauma (GBT). Hydroelectric dams generate TDG supersaturation that causes bubble growth in the tissues of aquatic animals, resulting in sublethal and lethal effects. We exposed fish to 100%, 115%, 120%, and 130% TDG at 16 and 63 cm of depth and recorded time to 50% loss of equilibrium and sublethal symptoms. Our linear model of the log-transformed time to 50% LOE (R2 = 0.94) was improved by including depth. Based on our model, a depth of 47 cm compensated for the effects of 4.1% (±1.3% SE) TDG supersaturation. Our experiment reveals that once the surface threshold for GBT from TDG supersaturation is known, depth protects rainbow trout (Oncorhynchus mykiss) from GBT by 9.7% TDG supersaturation per metre depth. Our results can be used to estimate the impacts of TDG on fish downstream of dams and to develop improved guidelines for TDG.

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>

Implications of gas content for predicting the stability of submarine slopes

1977 ◽  
Vol 2 (1-4) ◽  
pp. 81-100 ◽  
Author(s):  
Melvin I. Esrig ◽  
Robert C. Kirby
Keyword(s):  
Gas Content ◽  
The Stability
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