4. Cavitation similarity

4.1 Similarity coefficients

The (NPSH) _req of a pump is subject to the same laws of similarity as the total head H. As with the latter, we can define dimensionless coefficients that remain constant for geometrically similar pumps operating in similarity.

The development of cavitation figures can also be considered as following the classical laws of hydrodynamics. The laws of similarity for turbomachinery can be applied to the comparison between scale models and prototypes.

Two adimensional numbers characterize the (NPSH) _req , i.e. :

• Thoma's coefficient, designated σ and defined as the ratio of the...