Cavitation number

It has a similar structure as the Euler number, but a different meaning and use: The cavitation number expresses the relationship between the difference of a local absolute pressure from the vapor pressure and the kinetic energy per volume, and is used to characterize the potential of the flow to cavitate.

Researchers often aim to record cavitation inception at relatively low upstream pressures, particularly when they are pursuing non-destructive applications of this phenomenon.

As the development of cavitating flow progresses, the cavitation number steadily decreases until the system reaches the point of supercavitation, characterized by the highest achievable velocity and flowrate.

Following supercavitation, the system reaches its fluid-handling limit, even as upstream pressure continues to rise.

Consequently, the measured cavitation number embarks on an upward trajectory.

This trend is a recurring observation in numerous published articles within the literature.

) is a dimensionless quantity that can be used to predict cavitation in the suction of a pump.

It is named after German engineer Dieter Thoma (1881–1942).

The fluid will cavitate in the suction of the pump if the Thoma number is smaller than the critical cavitation parameter or the critical Thoma number defined as

is the net positive suction head required to prevent cavitation.

It is a parameter found experimentally for each pump model.