JWSS - Journal of Water and Soil Science

the impact of hydraulic loss on the performance of weirs should not be overlooked. In this study, a laboratory flume measuring 8 meters in length, 0.6 meters in width, and 0.6 meters in height was used to investigate the hydraulic loss of the weirs and their discharge coefficients. The weirs used in this research were of the labyrinth type, featuring both curved and linear designs. Dimensional analysis using the Buckingham method indicated that the discharge coefficient (Cd) relies on parameters such as the hydraulic head ratio (Ht/P), weir shape factor (Sf), hydraulic loss ratio (Hf/P), and Froude number (Fr). The results demonstrated that an increase in hydraulic head leads to a decrease in the discharge coefficient of the weirs. Furthermore, the intensity of flow blade interference over the weirs gradually increases the hydraulic loss with a rising hydraulic head. Hydraulic loss increases up to a certain level of hydraulic head before beginning to decline. Therefore, it can be stated that the hydraulic loss curve for weirs like ARCL exhibits a sinusoidal trend. At a hydraulic head ratio of 0.4, the ARCL weir experiences 227% more hydraulic loss compared to the APKW weir. At a hydraulic head ratio of 0.6, the RCL weir shows 200% more hydraulic loss than the PKW weir. The trend of hydraulic loss variation with increasing Froude numbers for ARCL and RCL weirs is also sinusoidal. The ARCL weir shows the highest hydraulic loss with increasing Froude number compared to the other weirs. All weirs modeled using FLOW-3D software showed values (Cd and Hf/P) that exceeded those from physical modeling, which is significant in terms of safety factors. Moreover, the error rate in numerical modeling varied based on different parameters and conditions, averaging between 10% and 30%. In some cases, labyrinth weirs exhibited higher error rates compared to piano key weirs.

One of the key challenges in the design of side weirs is enhancing discharge efficiency, which is defined as the dimensionless ratio of the flow rate over the weir to the total incoming discharge. This study investigates the hydraulic performance of a converging side weir equipped with flow-guiding side plates. A three-dimensional numerical model using FLOW-3D software was employed to simulate flow conditions in the presence of guide plates with varying angles, relative lengths (defined as the ratio of plate length to the upstream channel width), and installation positions, to identify hydraulically optimal configurations. Following validation of the model against experimental data, 28 different scenarios were evaluated. The results demonstrated that under proper conditions, the installation of side guide plates can significantly improve discharge efficiency. Among all cases, the configuration with a 60° deflecting angle and a relative length of 0.2, installed at the upstream location (X₁) of the weir, yielded the best performance, increasing efficiency from a baseline of 62% to 82%. Analysis of the velocity field further revealed that the formation of a low-velocity zone behind the plate plays a critical role in directing the flow toward the weir. Overall, the use of side guide plates presents a simple, low-cost, and effective solution for enhancing the hydraulic performance of converging side weirs without requiring structural redesign.