Vena contracta

In the case of both the free jet and the sudden pipe diameter change, the streamlines are unable to closely follow the sharp angle in the pipe/tank wall.

The converging streamlines follow a smooth path, which results in the narrowing of the jet (or primary pipe flow).

Measurement of the vena contracta is useful in echocardiography, where it describes the smallest area of the blood flow jet as it exits a heart valve.

This corresponds to the effective orifice area (EOA) calculated for heart valves using the continuity equation.

Several leading firms built this type of gun but it proved unpopular and most were returned to the manufacturers for large bore barrels.

Vena contracta
Just beyond the Swartswood Lake Dam, the river is forced to narrow by a concrete bridge support. Flow separation is evident at the sharp bend, just above the vena contracta