Cavitation Number

The Cavitation 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 Cavitation Number is useful when analyzing fluid flow dynamics problems where cavitation may occur.

The Cavitation Number can be expressed as

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

where

σ = Cavitation 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.