Abstract

Vertical lift tunnel gates are subjected to hydrostatic and hydrodynamic forces produced as a result of operating condition over a wide range of partial openings, discharge and heads. Among these forces is the unbalanced vertical hydrodynamic force resulting from the difference between the downward force on the top of gate within the gate shaft and the upward force on the gate bottom, the net resultant of these two forces is termed as a downpull force. The estimation of downpull force requires the determination of the top and bottom pressure coefficient (KT and KB) which affected by the geometry of gate bottom and the rate of flow passing over the top surface of gate. A two-dimensional CFD model is applied to predict a downpull coefficient (KT and KB) which is named as FLUENT program. The finite volume method is employed on a Reynolds averaged Navier-Stokes equations. The turbulence effects are simulated using the standard (k-ε) model. The simulation model is used for relevant experimental data obtained from hydraulic model tests conducted in laboratory for nine gate lip shape with nine gate openings for each gate lip geometry. The procedure is applied to estimate the pressure coefficients (KT and KB) for different gate bottom geometry. The results illustrate that the inclined gate lip shape with angle of (θ = 35o) given a minimum positive values of downpull force. Also, the downpull coefficient depends mainly on the magnitudes and the distribution of (KB) for a given value of (b2/b1). A general statistical model is built to predict the bottom pressure coefficient for any gate lip geometry.

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