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 Euler Number An introduction to and a definition of the Euler Number

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

The Cavitations Number can be expressed as

σ = ( p_r - p_v ) / (1/2 ρ v²)         (1)

where

σ= Cavitations number

p_r = reference pressure (Pa)

p_v = 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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