# Cavitation Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Cavitation number, abbreviated Ca, a 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 formulas

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

### Where:

 Units English Metric $$\large{ Ca }$$ = Cavitation number $$\large{ dimensionless }$$ $$\large{ U }$$ = characteristic velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ $$\large{ \rho }$$  (Greek symbol rho) = density of fluid $$\large{\frac{lb}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$\large{ p }$$ = local pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$ $$\large{ p_v }$$ = vapor pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$