Effects of Moved Dam Vertical Gate on Bottom Pressure Coefficien

Abstract

The vertical lift gate is the most commonly hydraulic gates used in controlling the flowrates of water in dam reservoir under a wide range of heads. Such gates are located at suitable section within the dam tunnel and moved vertically through a shaft, such gates are subjected to many hydraulic forces regarding the effects of high head of storage water in the reservoir of the dam. These forces are mainly represented by pressure coefficients, on top and bottom gate surfaces as top pressure coefficient and bottom pressure coefficient respectively. The difference between these two forces coefficient produces a major force coefficient so called down pull coefficient which has been considered as main measure to indicate the whole performance and stability of gate. Mostly these coefficients are estimated for stationary gate with specific ratios of gate openings. In current work, a hydraulic model is conducted to study the effects of moved gate with most common gate lip shape (θ=30°) and different discharges on bottom pressure coefficients which has more effective effects on hydraulic downpull force coefficient and hence on performance and stability of gate. The results showed that the bottom pressure coefficient is influenced effectively with moved gate and significant fluctuation is clearly observed with time. Such behavior may affect the stability of moved gate and caused many problems due to operation and safe closure.