Effects of Some Gate Lip Shapes on Downpull Force in Dam Tunnels

Abstract

The gate which controls the flow through the dam tunnel is termed as lift gate. Such gates are subjected to the hydrostatic and hydrodynamics forces, since the flow passes over and beneath the gate and produces pressures at the top and bottom of the gate surfaces. The differences between these two pressure forces are termed as downpull force. The evaluation of this force is very important due to its effects on closure of the gate, its positive and / or negative values. The estimation of downpull force requires the determination of top and bottom pressure coefficients for wide range of discharges, gate openings, velocity, and pressure distribution in many locations .For the present research these measurements have prepared for different types of gate lip shapes along with laboratory hydraulic tunnel model which have been used. Various flow conditions and gate openings have been examined .The results concluded from the measurements and analysis tend to confirm the effects of the gate lip shapes on the values of downpull force, which in case of its negative value will prevent the gate to close and make some failures and damages.