Cavitation parameter is defined by

A

$$\frac {P_v - P}{\frac {\rho V^2}{2}}$$

B

$$\frac {P_atm - P_v}{\frac {\rho V^2}{2}}$$

C

$$\frac {P - P_atm}{\frac {\rho V^2}{2}}$$

D

$$\frac {P - P_v}{\frac {\rho V^2}{2}}$$