Determination of the General Formula to Estimate the Discharge Quantity of Composite Structure for Free Flow

Abstract

River and open channel flow measurement is regarded as an important element in improving water system management. An experimental analysis in a laboratory flume has been executed to obtain formulas which can be used to predict the discharge quantity which crosses over the sharp crested weir and under the gate in the composite structure which is a tool of flow measurement. These formulas are applied for the free flow condition. Different configurations of composite structure have been used. These configurations have regular and irregular shapes. The derivation of the discharge quantity equation is based on the dimensional analysis which is employed to analyze the factors that control the operation of the composite structure. The family of formulas consists of eight formulas that are divided into two groups. The first group consists of four formulas which are derived based on the variable that dominates the hydraulic behavior of the composite structure, while the second group consists of four formulas based on the same variables of the first group but taking into consideration the effect of weir and gate shape by adopting the hydraulic radius of weir and gate. Based on the evaluation process, all formulas can be used perfectly well to predict the discharge quantity, regardless of the shape of weir and gate. On the other hand, based on the validation process, the formula that considered the effects of shape geometry, flow and fluid properties has given the best prediction of the discharge quantity.