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Topic: Cavitation

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	Cavitation - Wikipedia, the free encyclopedia
		Cavitation is a general term used to describe the behaviour of voids or bubbles in a liquid.
		Such cavitation often occurs in pumps, propellers, impellers,and in the vascular tissues of plants.Non-inertial cavitation is the process where a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field.
		Non-inertial cavitation is the process where small bubbles in a liquid are forced to oscillate in the presence of an acoustic field, when the intensity of the acoustic field is insufficient to cause total bubble collapse.
	en.wikipedia.org /wiki/Cavitation (1795 words)

	Sonic cavitation - Wikipedia, the free encyclopedia
		Sonic cavitation occurs when ultrasound waves passing through a liquid cause the formation of bubbles, a phenomenon known as cavitation.
		Examples of sonic cavitation include the sonicating water baths used to clean instruments and jewelry, as well as the laboratory technique sonication, used to emulsify mixtures or lyse cells.
		There are claims that sonic cavitation on a small but intense scale causes a form of cold fusion.
	en.wikipedia.org /wiki/Sonic_cavitation (239 words)

	Cavitation Detection in Hydraulic Turbines
		The term cavitation is used to describe the phenomenon of liquid-to-gas and gas-to-liquid phase changes that occur when the local fluid dynamic pressures in areas of accelerated flow drop below the vapor pressure of the local fluid.
		Cavitation commonly occurs in hydroelectric turbines, generally appearing around guide vanes, wicket gates, the turbine runner, and in the draft tube.
		Typically the raw signal is bandpass filtered for the desired high frequency band and the discovery of the hidden periodicity is accomplished through demodulation of the bandpassed signal using the principal of envelope detection.
	www.usbr.gov /pmts/hydraulics_lab/hydstructures/cavitate.html (1154 words)

	Acoustic cavitation (Site not responding. Last check: 2007-10-22)
		Cavitation inception is a threshold process and significantly depends on the presence of “nuclei” in the liquid.
		At the onset of inertial cavitation, bubbles oscillate violently, undergoing initial explosive growth and subsequent rapid collapse (Leighton 1994).
		Zhang and J. Duncan, "On the nonspherical collapse and rebound of a cavitation bubble," Phys.
	www.math.vt.edu /people/damir/texts/projects/drug_ac.html (2225 words)

	Cavitation Wear In Hydraulic Systems
		The formation of bubbles within liquids (cavitation) begins even in the presence of positive pressures that are equal to or close to the pressure of saturated vapor of the fluid at the given temperature.
		Cavitation wear is also known as cavitation erosion, vaporous cavitation, cavitation pitting, cavitation fatigue, liquid impact erosion and wire-drawing.
		Cavitation wear is a fluid-to-surface type of wear that occurs when a portion of the fluid is first exposed to tensile stresses that cause the fluid to boil, then exposed to compressive stresses that cause the vapor bubbles to collapse (implode).
	www.practicingoilanalysis.com /article_detail.asp?articleid=380&relatedbookgroup=Hydraulics (2005 words)

	Cavitation- and Erosion-Resistant
		Cavitation: In the literature and the field (and in this report), erosion caused by cavitation is generally referred to simply as cavitation.
		Cavitation is the progressive loss of original material from a solid surface due to the formation and collapse, within a liquid, of cavities or bubbles (ASTM G 32 1992).
		Low cavitation is defined as 1/16 to 1/8 inch-deep damage in carbon steel occurring in two year; medium cavitation is defined as more than 1/16 inch damage in austenitic stainless steel in 1 year; and high cavitation is defined as more than 1/8 inch damage in stainless steel in 6 months or less (Spicher 1994).
	www.cecer.army.mil /techreports/boycavit/boycavit.jef-05.htm (1968 words)

	Cavitation 5
		One pump with suction cavitation due to clogged intake screens, produced 86 decibels in the key of C. After the intake screens were cleared, the sound level dropped to 66 decibels in the key of C. NOTE: The key of C is commonly used to measure general noise.
		Suction cavitation has damaged the leading edge and suction side of the vane, and also damage is observed on "corner" surfaces leading into the vane.
		Suction cavitation on this pump was severe enough that cavities formed in the fluid before the fluid reached the impeller.
	www.irrigationcraft.com /diagnosing_cavitation.htm (1049 words)

	BVFD Fire Hydraulics-Cavitation
		Most fire department pump operators have a general idea of what cavitation is and some of the ways to go about reducing or avoiding it, but when probing beyond these very general concepts, knowledge seems to be somewhat limited in most cases.
		Implosions occurring during cavitation tend to break away or erode tiny pieces of metal from moving parts and from the pump casing.
		As stated earlier, cavitation occurs any time the pump tries to deliver more water than it is received thereby creating a vacuum on the suction side of the pump.
	webpages.charter.net /bourgvfd/pages/FireHydraulics/Cavitation.htm (1613 words)

	Cavitation,_SCAs_and_the_Proper_Maintenance_of Diesel_Engine_Cooling_Systems (Site not responding. Last check: 2007-10-22)
		Cavitation is the formation and collapse of air bubbles on the outside of the cylinder walls during combustion (does not apply to dry-liner engines).
		Cavitation is further aggravated by vibration of the cylinder liner.
		Cavitation bubbles are created at sites of low pressure as the liquid fractures or tears because of the negative pressure of the sound waves in the liquid.
	www.arrowheadradiator.com /cavitation,_scas_and_the_proper_maintenance_of_diesel_engine_cooling_systems.htm (1600 words)

	IDEX Corporation \| Micropump \| Tech Tips \| Cavitation
		Cavitation is a condition that occurs within a pump.
		Cavitation damage is caused by the shock waves created when the vapor cavities collapse near the elements in the pump.
		Cavitation occurs along stationary and moving elements in a pump.
	www.micropump.com /tech_tips/cavitation.asp (648 words)

	Fachbereich Physik der TU Darmstadt
		This is a cavitation field being produced by a radially symmetric sound field of approximately 23 kHz.
		Cavitation noise spectra as a function of the voltage of the driving piezoceramic cylinder.
		The frequency is scaled relative to the driving frequency of 71 kHz: Subharmonic frequencies and their harmonics appear upon increasing the driving amplitude.
	www.physik.tu-darmstadt.de /nlp/cavitation.html (212 words)

	Centrifugal Pump Cavitation - Engineers Edge (Site not responding. Last check: 2007-10-22)
		Cavitation in a centrifugal pump has a significant effect on pump performance.
		Cavitation degrades the performance of a pump, resulting in a fluctuating flow rate and discharge pressure.
		Noise is one of the indications that a centrifugal pump is cavitating.
	www.engineersedge.com /pumps/cavitation.htm (457 words)

	Cavitation
		Cavitation occurs in liquids when the local pressure is reduced to the vapor pressure of the liquid.
		While the NPSH (cavitation number) decreases, the cavity remains attached to the suction side of the blade but growing towards the blade to blade channel and down towards the hub (point 2).
		The development of cavitation is almost identical in the three passages of the inducer (figure 3-c).
	www.ansys.com /industries/tm-cavitation.htm (653 words)

	Centrifugal Pumps: Basic Concepts of Operation, Maintenance, and Troubleshooting (Part- II)
		The cavitation condition induced by formation and collapse of vapor bubbles is commonly referred to as Vaporous Cavitation.
		The cavitation condition induced by the formation and collapse of gas bubbles is commonly referred to as Gaseous Cavitation.
		The different types of cavitation, their specific symptoms and specific corrective actions shall be explored in the next part of the article.
	www.cheresources.com /centrifugalpumps2b.shtml (3839 words)

	Cavitation
		While propellers are examined most often, the cavitation tunnel is also used to assess the performance of appendages such as nozzles, rudders, stabilizer fins, fairings and brackets.
		Cavitation Erosion on a Model Ice-Class Propeller in Blocked Flow - Soft paint films were used to assess the likelihood of damaging erosion on a 200 mm diameter model of an open, fixed pitch propeller.
		Cavitation Erosion in Blocked Flow with a Ducted Ice-Class Propeller - Soft paint films were used to assess the likelihood of damaging erosion on a 200 mm diameter model of a ducted, controllable pitch propeller.
	www.oceaniccorp.com /ServiceDetails.asp?id=8 (446 words)

	CHIROWEB \| DC Archives - (Cavitation Emptor: Tracking the Holy Grail of Manipulation)
		In terms of where the actual cavitation was shown to occur, spinal manipulation was found to be accurate only half the time in the lumbar spine.
		However, the discrepancy between the target and the cavitation location was less than that observed in the lumbar spine.
		Certainly not in a position to jettison the entire concept of cavitation, since it represents a clear sequela for at least most manipulations and remains a plausible mechanism for initiating reflex responses.
	www.chiroweb.com /archives/22/19/27.html (1051 words)

	Chapter 7 - Cavitation and Bubble Dynamics - Christopher E. Brennen
		Such a structure is termed ``cloud cavitation.'' The temporal periodicity may occur naturally as a result of the shedding of cavitating vortices (see, for example, Figure 7.11), or it may be the response to a periodic disturbance imposed on the flow.
		This form of cavitation on a hydrofoil or propeller blade is usually termed ``sheet'' cavitation; in the context of pumps it is known as ``blade'' cavitation.
		Hart, D.P., Brennen, C.E., and Acosta, A.J. Observations of cavitation on a three-dimensional oscillating hydrofoil.
	caltechbook.library.caltech.edu /1/04/chap7.htm (7683 words)

	Cavitation
		Vortex Cavitation Inception : Vortex cavitation inception occurs when small bubbles experience a sharp pressure reduction due to capture by the core of a strong vortex causing the bubbles to grow explosively.
		Liquid remediation and disinfection: Cavitation bubble collapse in a liquid can generate extremely high local pressures and temperatures causing water to dissociate and form hydroxyl radicals, which are very strong oxidizing agents.
		Cavitation Erosion: The application of bubble dynamics to study material erosion is similar to the underwater explosion but at a smaller scale.
	www.dynaflow-inc.com /Services_DW/Cavitation_DW.htm (256 words)

	p990518a - Pulmonary Cavitation
		Title: Lung cavitation associated with Pneumocystis carinii infection in the acquired immunodeficiency syndrome: a report of six cases and review of the literature.
		Abstract: Cavitation following bland pulmonary infarction is not commonly considered in the differential diagnosis of cavitary lung disease.
		In nine patients the cavitation appeared rapidly (mean, 5 days) and was associated with fever, purulent sputum, and leukocytosis.
	www.emory.edu /WHSCL/grady/amreport/litsrch98/p990518a.html (823 words)

	Fluent News - Fall 2005 - Incipient Cavitation in a Steering Rotary Valve
		It is experimentally known [1] that cavitation occurs in certain locations inside the rotary valve, where the oil flows through a passage and there is an accompanying drop in pressure.
		Cavitation parameter, K, vs. fluid velocity for the case where the rotor is twisted by a torsion angle of 2° with respect to the stator; cavitation begins only after the point of incipient cavitation has been passed
		Beyond this point of so-called incipient cavitation, or Ki, as the velocity is increased, the cavitation intensity rises while the cavitation parameter, K, decreases.
	www.fluent.com /about/news/newsletters/05v14i3/a12.htm (776 words)

	WaterScienceNews.com -- Cavitation and Sonoluminescence
		Cavitation is used industrially to homogenize milk, paints, etc. One common method for mechanically inducing cavitation is to pump liquids through a mixing value which has a relatively small entry orifice and a much larger exit orifice.
		In some species of trees, the sound of cavitation is easily heard when air bubbles burst, bubbles that were formed from dissolved air in the water in the plant cells.
		Cavitation causes small bubbles to form around impurities in water, and low-energy sound waves cause the bubbles to expand then violently collapse.
	watersciencenews.com /sonolum.htm (1229 words)

	Cavitation
		Cavitation means that cavities are forming in the liquid that we are pumping.
		The cavities form for five basic reasons and it is common practice to lump all of them into the general classification of cavitation.
		High specific speed indicates the impeller eye is larger than normal, and efficiency may be compromised to obtain a low NPSH required.
	www.mcnallyinstitute.com /01-html/1-3.html (1425 words)

	Fluent NEWS - Fall 2004 - Horseshoe Cloud Cavitation
		For the first set of simulations performed, the transient calculation predicted the onset of cavitation, and revealed an initial fluctuation of the cavity volume, with a subsequent quasi-steady stabilization of a cavitation sheet.
		A typical “horseshoe” vapor structure – observed during the experiment and considered to be the driving mechanism for cavitation erosion – was correctly predicted by the simulation once the modifications were made.
		The results were found to be similar to the experimental findings, including significant dynamic cavitation near the front wall, with pulsations of the cavitation region and the separation of a cavitation cloud.
	www.fluent.com /about/news/newsletters/04v13i2/a7.htm (624 words)

	Cavitation In-Depth
		Under cavitation conditions water is one of the worst actors regarding equipment damage due to cavitation.
		Water is hard on equipment in cavitation conditions for at least two reasons: relatively high density (small molecular size and heavy molecular weight), and a sharp well defined phase change behavior.
		The combination of small heavy molecules and high cavity wall implosion velocities (resulting from the sharp and fast rate of phase change), results in the release of extreme inertial energies as the walls of the cavity strike against each other and against objects in the fluid flow path during the cavity implosion.
	www.irrigationcraft.com /cavitation_in_depth.htm (1000 words)

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