Effects of Gate Lip Shapes on Hydrodynamic Forces on Gate Dam Tunnels

Author : Thamir M.Ahmed1
1Civil Engineering Department, Ishik University, Erbil, Iraq

Abstract:  The lift gate is one of the major types of dam tunnel gates which is used to regulate the water flow transmitted from the reservoir to downstream side in order to satisfy several demand requirements. Due to pressurized flow, the upstream face, top and bottom surfaces of gate are subjected to hydrodynamics forces. As a result of gate openings, the downpull force is created from the difference between the downward force exerted by water passing over the top surface of gate and that established by the water jet beneath the gate. The estimation of downpull force is so important due to its significant effects on the movement and closure of the gate which in case of its negative value the gate may prevent to close and lead to some failures and damages.In the present study, the estimation of downpull force is made based upon the results of measurements which have been achieved by using hydraulic model of tunnel with different shapes of inclined gate lips with and without extensions. The pressure heads along the bottom and upper surfaces of gate, the upstream and downstream heads are measured in addition to the jet velocity for different gate openings. One of the main conclusions drawn from the measurements and analysis is that the effects of the gate lip shapes on the values of downpull force is significant, and the lip extensions with different ratios which were provided at trailing edge of gate have effectively contributed to reducing the downpull forces.

Keywords:  Lift Gate, Downpull Forces, Pressure Coefficients

doi: 10.23918/eajse.v3i2p47

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