Pressure Coefficients of Curved Lip of Vertical Lift Gate in Dam Tunnels

Abstract

The vertical lift gate shaft is installed across the dam tunnel to regulate the flow rate passing toward the downstream side to satisfy the water demand in addition to the power generation requirements. The flow through the shaft is mostly divided into two parts, over and below the gate, and as a result, two forces will be created, vertically ,downward and upward on both top and bottom gate surfaces. The difference between these forces produces so-called hydrodynamic force or hydraulic downpull force which has a vital effect on gate operation, so that in the case of negative values, this force will prevent the closure of the gate. The downpull force influences by many parameters, however, the geometry of gate is considered as one of the most common effective factor that influence the values and behavior of downpull force. In present study, physical hydraulic model is used to assess the effects of different rounded gate lip shapes on downpull force with respect to different gate opening ratios. The variation of bottom pressure coefficient along the gate surface has also been studied and the results are discussed.