Three-Dimensional Open Channel Flow

by Chao-Lin Chiu, (M.ASCE), Prof. of Civ. Engrg.; Univ. of Pittsburgh, Pittsburgh, Pa.,
Hsin-Chi Lin, Engr.; Bernard Johnson, Inc., Washington, D.C.; formerly, Research Asst., Dept. of Civ. Engrg., Univ. of Pittsburgh, Pittsburgh, Pa.,
David E. Hsiung, Research Asst.; Dept. of Civ. Engrg., Univ. of Pittsburgh, Pittsburgh, Pa.,

Serial Information: Journal of the Hydraulics Division, 1978, Vol. 104, Issue 8, Pg. 1119-1136

Document Type: Journal Paper


An open channel flow is usually three-dimensional consisting of the primary and secondary flows. The primary flow is defined herein as the flow component in the longitudinal direction of the channel, while the secondary flow includes the remaining flow components in the vertical and transverse directions of the channel. In an alluvial channel the channel cross sections and, thus, the three-dimensional flow structure vary irregularly or randomly along the flow. A technique has been developed and presented herein that can be used to compute secondary currents and, thus, the irregular three-dimensional structure of open channel flow. The technique uses analytical, hydrodynamic equations along with measured data of channel geometry and primary flow velocity distribution. Illustrative examples are presented with results of practical applications of the technique, describing the variability of the direction and magnitude of secondary currents with time, space, and discharge rate.

Subject Headings: Three-dimensional flow | Open channel flow | Alluvial channels | Secondary flow | Flow measurement | Flow distribution | Velocity distribution | Cross sections

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