Answer / baburao

cavitation is formation of air bubbles due to decrease in
water pressure below its vapor pressure

Answer / sivaramakrishnan.a.v.

Cavitation is a phenomenon whereby liquid flowing through a
a valve or pump under reduced pressure(below vapour
pressure)will form gaseous bubbles that will collapse upon
pressure recovery prodcing potential damage to the valve or
pump internals leading to premature failure .Ie the
pressure drops below the vapour pressure leading to
formation of vapour bubbles and tries to increase above the
vapour pressure.This is sserious concern in high pressure
drop applications.

Answer / karthick

when the liquid pressure in the pipe falls below vapour
pressure vapour gas bubbles form.this is known as
cavitation.

Answer / shahnawaz

when the pressure inside the pump equals the vapour
oressure of water. water will starts evaporating and cause
bubbules inside the pump

Answer / naseeb ahmeds

THE BOILING TEMPRETURE OF LIQUID DEPENDS ON PRESSURE OF
LIQUID,ITS VALUE INCREASES WITH INCREASE IN PRESSURE.THUS IF
THE PRESSURE OF LIQUID FLOWING THROUGH IS LOWERED,DUE TO
CERTAIN CIRCUMTANCES,THE FLOWING LIQUID WILL BOIL AT
PREVALENT ROOM TEMP.THE BOILING OF LIQUID RESULTS IN
FORMATION OF BUBBELES,WHICH THEN TRAVEL DOWN STREAM
RESULTING IN TWO PHASE FLOW.IN ACTUAL PRACTICE FORMATON OF
BUBBELES TAKES PLACE DUE TO DISSOLVE GASES IN THE FLOWING
LIQUID.THE BUBBLE FORMATION IN FLOWING LIQUID IS CONSIDERD
AS POINT OF CAVITATION INCEPTION

Answer / bn

when the local pressure in a liquid falls below the vapour
pressure, for that temperature, the liquid boils locally
and forms bubbles; this is flashing.
If the pressure subsequently increases, the bubbles colapse
violently; this is cavitation.
If the liquid contains dissolved gases, when the local
pressure is reduced gas bubbles will form before the liquid
starts to boil.
If the pressure is subsequently increased, the gas bubbles
will colapse but much slower than the colapse of a vapour
bubble. This is pseudo-cavitation.
It is the colapse of vapour bubbles which causes noise,
vibration and local damage. Pseudo-cavitation may not do
much damage to rotodynamic pumps. Pseudo-cavitation will
destroy some pd pumps just like cavitation. Pump operating
conditions, pumped liquid and pump design are critical
factors.

Answer / shaktisinh zala

When the absolute pressure at some point in a liquid
reaches the vapour pressure corresponding to the liquid
temperature there, bubbles, cavities, form within the
liquid at this point. These cavities contain vapour and
possibly some gases coming out of solution. When the liquid
is in motion and a pressure increase occurs without a
substantial change in temperature, as in the case of flow
through a running impeller, the vapour in the bubbles
cannot be sustained, it condenses very rapidly and
therefore the bubbles collapse quite suddenly, giving rise
to shocks in the nature of implosions. This phenomenon is
called cavitation.

The formation of bubbles gives rise to hydraulic
performance reduction possibly to an unacceptably large
scale,to rough running and possibly to noise. As the vapour
bubbles collapse in an extremely short period of time, in
microseconds, pressure shocks traveling at the local speed
of sound, meet the metallic boundaries at very high local
surface pressure that can be higher than the ultimate
strength or fatigue limit of the material, causing material
break up, pitting and erosion followed by corrosion. The
damage is more extensive if the bubbles implode on the
metallic boundaries.
The pressure of the liquid going into a centrifugal pump
drops as it flows from the suction pipe through the suction
nozzle and into the impeller. The pressure drop is a
function of many factors, including pump geometry,
rotational speed, frictional and hydraulic shock losses,
and rate of flow.
If the pressure at any point within the pump falls below
the vapor pressure of the liquid being pumped, vaporization
and so bubble formation will occur. As the pressure
increases the local pressure is above the vapour pressure
and so the bubbles collapse spontaneously and cavitation
occurs
When cavitation occurs due to insufficient head at the pump
suction
the type of cavitation taking place is termed Normal
Cavitation.

Normal Cavitation results in:-
Pump performance deterioration - reduction in total head
developed,
flowrate reduction, pump efficiency reduction.
Increase in the level of pump vibrations and of noise
level, flowrate
pressure and power input fluctuations if the cavitation
is severe
enough.
Pump impeller and possibly casing pitting and erosion.

In carrying out cavitation tests (constant speed and
flowrate but
decreasing suction head) the point at which the total head
developed falls by a predetermined amount (usually 3%) is
regarded
as the point at which the pump becomes critical

Answer / arindam dutta

When water flows through a pipe, it often happens that at
certain places the local pressure lessens than the vapour
pressure. this is called cavitation and causes serious
pitting.

Answer / s.khan

any vapor bubbles formed by the pressure drop at the eye of
impeller are swept along the impeller vanes by the flow of
fluids, when bubbles enter in a region where local pressure
is greater then saturation pressure,further out the impeller
vane.the vapor bubble abruptly collapse.this process of the
formation and subsequent collapse of vapor bubble in a pump
is called cavition

Answer / marrion stewart

Cavitation is the procees by which vapour or gas bubbles
are fomed in water that is under tension. This will create
a process called embolism where by the stretching strength
of water will be exceeded causing disruption of the
hydraulic continuity of the soil pore, xylem and tracheids

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