On establishing uniform channel flow with tail gate

Steady uniform flow is a basic reference condition for hydraulic analyses of water surface profiles, resistance, velocity and pressure distributions, and channel geometry effects for open-channel flows. In laboratory experiments uniform flow is often generated by adjusting tail and entrance gates such that the flow depth remains constant along the channel. This note shows that the constant depth criterion is necessary, but insufficient, to obtain a true uniform flow for which cross-sectional flow velocity and stress distributions should also remain unchanged for a short reach around the measurement section.