# Flow velocity

The average flow velocity is the quotient of the volume flow through the cross-sectional area under consideration.

v = Q / A

v - Average flow velocity
Q - Flow rate
A - Area flowed through

For a circular cross section, the following results are obtained with

A = p / 4 - D2

v = 4 - Q / (p - D2)

D - Diameter of the circular area flowed through (internal pipe diameter)

c or v are usually used as symbols for the average flow velocity. Often v is used for the local velocity, while c is used as a symbol for the mean velocity. The DIN 24260 provides the symbol v for the average speed.

The average flow velocity is an important parameter when selecting the optimum pipe diameter for a new pipeline.

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