Brink Depth At Free Overfall in Open Channel Analysis : A Review

Many devices are fabricated to measure discharge in open channel. The flow over a free overall (brink phenomenon) can be used as a device to measure discharge in open channels with known the end depth. This paper presents mathematical studies to evaluate efficiency of the brink as device of measuring flow rate in horizontal, mild and adverse open channels. The general mathematical model is derived using momentum, discharge and Froude number equations for horizontal, mild and adverse slopes open channels. A proposed mathematical model is calibrated by previous experimental data. Equation gives accurate discharge from known end water depth. The characteristics include, water depth over free overfall, critical and brink depthat lip of free overfall, the effect of bed roughness of free overfall on flow depths (normal, critical and brink depth) we obtained a relation between these depths and compared the those with results without roughness for the same discharges. A free overfall at the end of the channel is used as a flow measuring device. In this paper, theoretical end depth ratio (EDR) and end depth discharge (EDD) relationships have been studied. Despite the many theoretical studies carried out in channels having different cross-section shape, slope, and roughness, the problem of the free overfall as a flow measuring device has not been completely solved, and other studies are needed. A theoretically based end-depth-discharge relationship is obtained for both subcritical and supercritical flow in rectangular, triangular, circular, U-shape and trapezoidal channels. For each cross-section shape, discharges predicted using the theoretical relationship.