# Cavitation Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Cavitation number ( $$Ca$$ ) (dimensionless number) expresses the relationship between the difference of a local absolute pressure from the vapor pressure and the kinetic energy per volume.

### Cavitation Number FORMULA

$$\large{ Ca = \frac { 2 \left(p \;-\;p_v \right) } {\rho U^2} }$$

$$\large{Ca = \frac { \left(p \;-\;p_v \right) } { \frac {1}{2} \rho U^2} }$$

Where:

$$\large{ Ca }$$ = Cavitation number

$$\large{ U }$$ = characteristic velocity

$$\large{ \rho }$$  (Greek symbol rho) = density of the fluid

$$\large{ p }$$ = local pressure

$$\large{ p_v }$$ = vapor pressure

Solve for:

$$\large{ p = \frac {Ca \rho U^2} {2} \;+\; p_v }$$

$$\large{ p_v = p \;-\; \frac {Ca \rho U^2} {2} }$$

$$\large{ \rho = \frac { 2 \left (p \;-\;p_v \right)} {Ca U^2} }$$

$$\large{ v = \sqrt { \frac { 2 \left (p \;-\;p_v \right)} {Ca U^2} } }$$