Discharge prediction model for flow through differential weir-gate structures

Abstract

This study experimentally investigates a weir-gate structure that combines a rectangular opening at the base of a rectangular sharp-crested weir. This device integrates the functions of individual weirs and gates while addressing the challenges associated with each. The reported literature lacks investigations on rectangular sharp crested weir-gates with varying weir crest lengths and gate openings. To address this gap, the current study explored the hydraulic performance of such uniquely configured weir-gate structures, herein named as Differential Weir-Gates (DWG). The objective was to develop a discharge prediction model applicable to DWG (simultaneous overflow and underflow), as well as to individual weir (only overflow) and gate (only underflow) scenarios. Experiments have been conducted on 29 different DWG models with variations in weir height, gate opening, and length of weir crest. A functional relationship was established using combination of the dimensional analysis and the continuity equation. Finally, the proposed discharge model was developed through Multiple Linear Regression (MLR), demonstrating relative errors under ±10 % with an absolute mean relative error of 1.71 %. The proposed model was further evaluated using statistical indices including Coefficient of Determination (R²), Root Mean Squared Error (RMSE), and Kling-Gupta Efficiency (KGE). In comparison to the limited existing discharge models in the literature, the proposed discharge model exhibited better accuracy in predicting discharge. The proposed discharge model was slightly modified to accurately predict the discharge through a weir-gate having trapezoidal weir and rectangular gate sections as well. The surface tension effects were observed to be dominant for lower values of Weber numbers. Overall investigations indicated that the proposed discharge model can be used for accurate discharge predictions of individual weir, individual gate, and DWG with both rectangular and trapezoidal weir sections for the range of variables investigated in present study. This versatility offers significant advantage for hydraulic engineers working with weir-gates.