Author(s): B. T. A. Sagar

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Abstract: Severe hydrodynamic problems on low-head weir gates are not common. But the writer came across two peculiar cases of hydrodynamic problems of surprising nature. In the first case, the gates were vibrating so severely as to shake and threaten the stability of the weir and the bridge. Investigating the causes and identifying the areas of turbulent flow which induced vibrations resulted in implementing simplified solutions. The bottom seal was replaced by a sharp rectangular vertical seal. The bottom shape of the gate was modified by providing a 45 degree converging plate enclosing the upstream gate members protruding into flow and, thus, preventing the flow disturbance. In the second case, a weir gate with top seal and orifice flow repeatedly tilted sideways during lowering operation under gravity at a particular gate position and got jammed. The cause could be identified as (a) change of flow from free fall to orifice type at the particular gate position causing sudden downpull force, and (b) unequal spring tightness on the wire ropes on either side of the gate. The remedial measures consisted of (a) changing the gate bottom shape to avoidd downpull, (b) replacing springs by turnbuckles on wire ropes, which can be tightened equally.

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Year: 1999