Cavitations Number

An introduction to and a definition of the Cavitations Number

The Cavitations Number or Cavitation Parameter is a "special edition" of the dimensionless Euler Number.

The Cavitations Number is useful analyzing fluid flow dynamics problems where cavitations may occur.

The Cavitations Number can be expressed as

σ = ( pr - pv ) / (1/2 ρ v2)         (1)

where

σ= Cavitations number

pr = reference pressure (Pa)

pv = vapor pressure of the fluid (Pa)

ρ = density of the fluid (kg/m3)

v = velocity of fluid (m/s)

To prevent cavitation

  • avoid low pressure - pressurize supply tanks if necessary
  • reduce fluid temperature
  • use larger suction pipe diameters - reduce minor losses
  • use cavitation resistant materials or coatings
  • small amounts of air supplied to the suction system may reduce the amount of cavitation damage
  • keep available NPSH well above required NPSH.

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