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Circumferential speed

The circumferential speed (u) is the velocity of a point particle performing a circular motion. This can be a point particle of a rotating pump shaft or a rotating impeller. The following relationship exists between the radius (r) of the point particle and the angular velocity (ω):

u = r • ω

In turbomachinery design, the circumferential speed (u), together with the relative velocity (w) and the absolute velocity (c) form the velocity triangle.

The circumferential speed at relevant locations of the impeller has a marked influence on the suction characteristics, noise development and strength of the rotating components of centrifugal pumps.

Typical circumferential speeds (at the impeller outlet) range between 20 and 60 m /s, in exceptional cases up to 140 m /s.

Circumferential speed