Flow Velocity: The Chézy Formulation

Open-channel flow velocity is proportional to shear velocity.

Learning Goals

  • Relate flow velocity to shear velocity via the Chézy Formula.
  • Understand its relationship to flow depth and the eventual reframing of the Chézy coefficient by Manning to take flow depth into account.

The formula

For quick reference; see course notes and video for derivation:

\[\bar{u} = C_z u_\tau\]

For steady, uniform flow:

\[\bar{u} = C_z \sqrt{g h S}\]

Course notes

Flow mechanics PDF

Chézy’s formula explained



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