Effects of Gate Lip Orientation on Bottom Pressure Coefficient of Dam Tunnel Gate

Vertical-lift tunnel-type gates are subjected to hydrostatic and hydrodynamics forces created as a result of operation conditions of a wide range of partial openings, discharges and heads. Among these forces is the uplift hydrodynamic force resulting from the effects of flow issuing below the gate bottom. The evaluation of this force requires the determination of bottom pressure coefficient ( K b ) which is based mainly upon the measurements of the jet flow velocity across the vena contracta, the pressure head distribution along and across the bottom gate surface and pressure head of flow just downstream the gate shaft. In the present research, a random hydraulic model was created to identify the effect of twelve gate lips orientation on the behavior of flow and consequently on the bottom pressure coefficient. The main conclusion is that the values of bottom pressure coefficient ( K b ) are inversely proportional to gate opening ratios ( Y / Y 0 ) and range from high values with small gate openings ratios and low values for ( Y / Y 0 > 30%). The study finds that the bottom pressure coefficient ( K b ) and the fluctuations flow pattern below the gate surface are influenced mainly by the gate geometry.