Extensional Flow of Liquid Jets Formed by Bubble Collapse in Cavitating Motor Oils

2002 ◽  
Author(s):  
P. R. Williams ◽  
M. S. Barrow ◽  
S. W. J. Brown
Keyword(s):  
Extensional Flow ◽  
Bubble Collapse ◽  
Liquid Jets ◽  
Motor Oils

Rheology of Dilute Polymer Solutions and Engine Lubricants in High Deformation Rate Extensional Flows Produced by Bubble Collapse

2004 ◽  
Vol 126 (2) ◽  
pp. 162-169 ◽  
Author(s):  
M. S. Barrow ◽  
S. W. J. Brown ◽  
S. Cordy ◽  
P. R. Williams ◽  
R. L. Williams
Keyword(s):  
Xanthan Gum ◽  
Extensional Flow ◽  
Journal Bearings ◽  
Bubble Collapse ◽  
Liquid Jets ◽  
Pressure Waves ◽  
Polymeric Additive ◽  
High Deformation Rate ◽  
High Deformation ◽  
Dilute Polymer Solutions

We report a study of liquid jets formed by the collapse of bubbles under cavitation-generated pressure waves. Such jets involve an extensional flow which is characterized by high rates of extension, the latter being relevant to considerations of the flow of oils within dynamically loaded journal bearings. The technique reported here is found to be sensitive to the influence of extremely small concentrations of high molecular weight polymeric additive (xanthan gum). Commercial multigrade oils are also found to exhibit significantly larger resistance to extensional flow than their Newtonian counterparts and, insofar as the multigrade oils studied here are made viscoelastic by polymer additives, and possess significant levels of resistance to extension, the results provide evidence in support of a mitigating effect of viscoelasticity on cavitation, as mooted by Berker et al. [3].

Flow of multigrade motor oils in an extensional flow field

1990 ◽  
Vol 34 (8) ◽  
pp. 1373-1386 ◽  
Author(s):  
R. K. Gupta ◽  
R. C. Chan ◽  
A. K. Deysarkar
Keyword(s):  
Flow Field ◽  
Extensional Flow ◽  
Motor Oils

Cavitation Erosion in a Thin Film as Affected by the Liquid Properties

1971 ◽  
Vol 93 (4) ◽  
pp. 470-477 ◽  
Author(s):  
F. F. Tao ◽  
J. K. Appledoorn
Keyword(s):  
Thin Film ◽  
Cavitation Erosion ◽  
Environmental Control ◽  
Ambient Pressure ◽  
Atmospheric Environment ◽  
Bubble Collapse ◽  
Liquid Jets ◽  
Gas Solubility ◽  
Vapor Pressures ◽  
Reduced Pressures

The effect of liquid properties and the atmospheric environment on cavitation erosion was investigated in a thin film cavitation apparatus which consists of an ultrasonic horn with a flat tip vibrating against a stationary 1/2 in. ball at a frequency of 20 KC. The experimental results show that cavitation erosion is less severe for liquids of higher gas solubility or at vapor pressures greater than 100 torr. It is therefore possible to reduce the damage by blending a light component in lubricants or liquids and/or by environmental control. The effect of ambient pressure was also observed by tests in vacuum and under various reduced pressures up to one atmosphere. The damage increases with the increase of pressure. These results indicate that the most important factor in cavitation erosion is the differential pressure inside and outside the cavities, with the dissolved gases and/or vapor serving to control this pressure differential. The investigation of cavitation erosion with liquids of various properties also provides information for the understanding of the erosion mechanism. Evidence was obtained which supports the theory that the damage is caused by fatigue failure attributable to the impingement of liquid jets during bubble collapse. The liquid properties may control the jets velocity and thus affect the applied stress on surface boundaries.

High Deformation Rate Uniaxial Elongation Flow of Mobile Fluids in Cavitation Bubble Collapse Experiments

2003 ◽  
Author(s):  
P. Rhodri Williams ◽  
Matthew S. Barrow ◽  
Stephen Cordy ◽  
Karl Hawkins
Keyword(s):  
Journal Bearing ◽  
Extensional Flow ◽  
Significant Degree ◽  
Bubble Collapse ◽  
High Deformation Rate ◽  
High Deformation ◽  
Uniaxial Elongation ◽  
Elongation Flow ◽  
Low Shear Viscosity ◽  
Low Shear

We report experimental work involving the rapid uniaxial elongation of jets of mobile (i.e. low shear viscosity) liquids formed by the collapse of a gas bubble under a cavitation-generated shockwave. The results of this work establish that the jets experience a significant degree of extensional deformation, at high rates of extension (typically > 1000 s−1) which are relevant to considerations of journal bearing lubrication. The results of experiments conducted on samples of commercial multigrade motor lubricants in the 15W40 category indicate a substantially increased resistance to extensional flow when compared with the behaviour of their Newtonian counterparts. Interestingly, the technique is able to distinguish between the rheological properties of lubricants of identical category (15W40) which are formulated for use in different engines (petrol engine and diesel engine, respectively). The lubricant formulated for the latter application is found to exhibit the highest resistance to extensional flow.

scholarly journals The Use of Cavitating Jets to Oxidize Organic Compounds in Water

2000 ◽  
Vol 122 (3) ◽  
pp. 465-470 ◽  
Author(s):  
K. M. Kalumuck ◽  
G. L. Chahine
Keyword(s):  
Organic Compounds ◽  
Acoustic Waves ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Hydrodynamic Cavitation ◽  
Bulk Solution ◽  
Bubble Collapse ◽  
Liquid Jets ◽  
Recirculating Flow ◽  
Local Pressures

Exposure to ultrasonic acoustic waves can greatly enhance various chemical reactions. Ultrasonic acoustic irradiation of organic compounds in aqueous solution results in oxidation of these compounds. The mechanism producing this behavior is the inducement of the growth and collapse of cavitation bubbles driven by the high frequency acoustic pressure fluctuations. Cavitation bubble collapse produces extremely high local pressures and temperatures. Such conditions are believed to produce hydroxyl radicals which are strong oxidizing agents. We have applied hydrodynamic cavitation to contaminated water by the use of submerged cavitating liquid jets to trigger widespread cavitation and induce oxidation in the bulk solution. Experiments were conducted in recirculating flow loops using a variety of cavitating jet configurations and operating conditions with dilute aqueous solutions of p-nitrophenol (PNP) of known concentration. Temperature, pH, ambient and jet pressures, and flow rates were controlled and systematically varied. Samples of the liquid were taken and the concentration of PNP measured with a spectrophotometer. Experiments were conducted in parallel with an ultrasonic horn for comparison. Submerged cavitating liquid jets were found to generate a two order of magnitude increase in energy efficiency compared to the ultrasonic means. [S0098-2202(00)00303-5]

Elastic Effects in Liquid Jets Formed by Bubble Collapse

1998 ◽  
pp. 511-512
Author(s):  
P. R. Williams ◽  
S. W. J. Brown ◽  
P. M. Williams
Keyword(s):  
Bubble Collapse ◽  
Liquid Jets

On Cumulative Collapse of Cavitation Cavities

1968 ◽  
Vol 90 (1) ◽  
pp. 116-124 ◽  
Author(s):  
S. P. Kozirev
Keyword(s):  
Cavitation Bubble ◽  
Water Jet ◽  
Bubble Collapse ◽  
Liquid Jets ◽  
Jet Formation ◽  
Model Based ◽  
Jet Impact

Highly nonsymmetrical bubble collapses are viewed photographically, and it is noted that the collapses occur in such a fashion as to produce liquid jets. These are considered as similar to shaped charges used in explosives, and a model based on cumulative jet formation is postulated to explain the damaging power of such collapses. The damage from cavitation bubble collapse is examined and found to be similar to that from water jet impact.

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