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nukk41df · Posted: Tue 15:40, 15 Oct 2013 Post subject: hollister france Cavitation Issues

Cavitation is the [url=http://www.jeremyparendt.com/Hollister-b5.php]hollister france[/url] condition where gas bubbles form within a liquid flow as a result of the liquid pressure falling below the fluids vapor pressure. There are two types of cavitation inertial cavitation (also known as transient cavitation) and non-inertial cavitation. In either case, cavitation is not desirable and pump design seeks to minimize the impact of the condition.

Inertial Cavitation

This type of cavitation occurs when the series of bubbles within the fluid are forming and collapsing in rapid succession. The sudden collapse creates a shock wave and this form of cavitation is frequently observed in pumps, propellers, control valves and impellers.

The shock waves produced are of sufficient strength to cause damage to the mechanism and working parts, and for this reason considerable design and testing efforts are made to reduce and eliminate the condition. Cavitation, and dealing with the adverse consequences of the phenomenon, forms a major part of fluid dynamics.

Cavitation inception is where a fluid is subjected to a pressure which is low enough for a void or bubble to form. Such low pressure conditions can be found behind any object which is vibrating underwater or within a fluid, e.g. behind the blade of a propeller. The bubble then collapses due to the relatively higher pressure of the enclosing fluid, which increases the pressure (and temperature) within the bubble. The void formed [url=http://www.mxitcms.com/abercrombie/]abercrombie milano[/url] is not a [url=http://www.mnfruit.com/doudounemoncler.php]moncler[/url] perfect vacuum because evaporation from the fluid into the void occurs, though at relatively very low pressure. As the bubble collapses, the gaseous vapor is dissipated into [url=http://www.jeremyparendt.com/Barbour-Paris.php]barbour france paris[/url] the surrounding fluid in a violent action which [url=http://www.gotprintsigns.com/abercrombiepascher/‎]abercrombie pas cher[/url] also causes the release of energy (the acoustic shock). It comes as a surprise for many to learn that the temperature and pressure may reach extremely high levels (thousands of degrees [url=http://www.lcdmo.com/hollister.php]hollister pas cher[/url] Kelvin and hundreds of atmospheres), [url=http://www.rtnagel.com/airjordan.php]jordan pas cher[/url] but this is at the point where the void has contracted to a very small fraction of its original size.

Cavitation resembles [url=http://www.mnfruit.com/airjordan.php]jordan pas cher[/url] boiling, however there are different thermodynamic paths followed in creating the fluid vapor. In boiling, vapor is created as a consequence of vapor pressure rising above the ambient pressure and there is enough energy to cause the phase change. On the other hand, the gaseous vapor associated with cavitation inception is created due to a drop in ambient pressure falling below the fluids tensile strength.

For cavitation inception, a surface of some description is required to allow the cavitation bubbles to nucleate. For this reason, using materials in pump, impeller and propeller construction which are hydrophobic (in the case of water), will stabilize the cavitation and reduce the adverse effects [url=http://www.rtnagel.com/louboutin.php]louboutin pas cher[/url] of the phenomenon.

Non-inertial Cavitation

This form of cavitation comprises bubbles in a fluid which are oscillating due [url=http://www.teatrodeoro.com/hollisterde.php]hollister deutschland[/url] to an energy input. It is this principle which is used in the mechanism for ultrasonic cleaning baths, however this phenomenon is also seen with pumps and propellers too.

Consequences

Cavitation is responsible for several, serious and [url=http://www.moncleroutletosterblade.com]moncler outlet[/url] undesirable consequences including noise, damage to working parts and components, excessive vibration and is a cause of mechanical inefficiency. In some applications, particularly military, e.g. submarine propellers, the consequences are mission critical.

The energy released during cavitation is relatively small, however localized cavitation over time will result in excessive wear and tear on components. Pitting is a frequent mark of cavitation and once an area is affected the damage [url=http://www.mnfruit.com/airjordan.php]jordan[/url] tends to accelerate until failure. In addition, the pitting of the surface also creates nucleation sites for further bubble creation, and stress corrosion is commonly associated with cavitation due to the weakening effect upon the material.
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