Experimental and numerical study of the discharge capacity of a labyrinth side weir in a straight channel.

A side weir is a weir placed in the side wall of a channel. There are several functions performed by side weirs, including raising water levels for irrigation and drainage and diverting excess flow from rivers or channels during floods, which can help address major problems during the rainy season. In this study, side weir discharge coefficients in trapezoidal labyrinths of different side wall angles (15°, 30°, 45°, 60°, and 75°) and a linear side weir (90°) placed in the side wall of a rectangular channel was calculated in the laboratory. A hydraulic design and analysis approach for side weirs was first developed using experimental data from six physical models, and the locations in which these models were installed in the side wall of the straight channel and the discharge coefficient for each model were calculated by establishing the relationship between the discharge entering the main channel and the value of the head above each weir. Five values were taken from the discharge for five values from the head above the side weir, allowing the development of several equations in addition to the identification of the relationships through which the discharge coefficient was calculated. In addition, CFD software using a K-omega-SST turbulence model was used to simulate the side weirs, with the volume of fluid (VOF) scheme used to simulate changes in flow at the free surface. As a result, the CFD model was able to effectively predict changes in free surface flow, with results that demonstrate that the discharge coefficient Cd rises as the side wall angle increases and falls as the side wall angle decreases. This means that a trapezoidal labyrinth side weir with a side wall angle of 75° has a discharge coefficient greater than that of the other investigated weirs, and that the discharge coefficient increases as the shape approaches the shape of a straight weir. Significant agreement between the data from the lab and the simulations was also observed. [ABSTRACT FROM AUTHOR]