Hydraulics of flow over triangular weirs of finite crest length in free and submerged flow conditions

Abstract

A comprehensive analysis on the hydraulics of flow over Triangular Weirs of Finite Crest Length (TWFCL) with both a sharp and a round upstream entrance was performed in free flow, modular limit, and submerged flow conditions. Many researchers studied the hydraulics of flow over TWFCLs and proposed empirical formulations that require iterative methods or need some parameters such as boundary layer thickness and Froude number which are difficult to estimate in the field. This study used the available data in the literature and proposed direct correlations between the apex angle, θ, and discharge coefficient, C_d, using a multi-regression analysis. The proposed non-linear formulation for prediction of discharge coefficient has an average variation of 3 % with experimental data for TWFCL with a round upstream edge and it is applicable for 30^o ≤ θ ≤ 90^o. A linear model was proposed for prediction of discharge coefficient in TWFCL with larger apex angles with an average variation of less than 2 %. The variation of modular limit with normalized water head indicated that TWFCLs are more resistant to the downstream water level raise than that of classic weirs of finite crest length. The effects of weir's geometry on variations of discharge reduction factor with the submergence ratio was found to be negligible in TWFCLs. A non-linear model was proposed to predict discharge reduction factor of TWFCL which was independent of weir's geometry and θ.