Experimental Study of Pressure Coefficient along Inclined Bottom Surface of Dam Tunnel Gate

Abstract

The major reason behind lift vertical gate installation within the dam tunnel is to provide the specific amounts of water released from the reservoir under a wide range of head variations. For such hydraulic structures, the water is flowing in two directions, below the gate which produce uplift force and above the gate through gate shaft which caused vertical downward force. The difference between these two hydrodynamic forces produces downpull force which affects the operation and stability of the gate. Moreover, the gate is subjected to different patterns of flow, especially along the bottom surface, and consequently, the attachment and reattachment of flow lead to vibrate the gate and create a significant challenge to its stability.
The analysis of the downpull forces and flow conditions effects is based upon the prediction of bottom pressure coefficients which are influenced mainly by many parameters such as pressure head distribution, jet velocity head and geometry of lip gate. In present research the results of all related measurements of physical hydraulic model were analyzed and presented by using three-dimension presentation to study the behavior of water flow pattern below the gate and hence the generation of pressure for inclined lip gate 
geometries (θ=55°). The measurements of upstream head, downstream head, jet velocity and peizometric heads distribution along and across the gate bottom surface are involved. The main conclusion states that the bottom pressure coefficient is significantly influenced by the lip gate shapes and gate openings.