The Euler number is a dimensionless number used in fluid flow calculations. It expresses the relationship between a local pressure drop e.g. over a restriction and the kinetic energy per volume, and is used to characterize losses in the flow, where a perfect frictionless flow corresponds to an Euler number of 1.
It is defined as
where
- is the density of the fluid.
- is the upstream pressure.
- is the downstream pressure.
- is a characteristic velocity of the flow.
The cavitation number has a similar structure, but a different meaning and use:
The Cavitation number is a dimensionless number used in flow calculations. It 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.
It is defined as
where
- is the density of the fluid.
- is the local pressure.
- is the vapor pressure of the fluid.
- is a characteristic velocity of the flow.
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