Preliminary Experimental Study on the Effect of the Sediment-Laden River on WES Practical Weir’s Discharge Capacity

In general, the discharge capacity of hydraulic structures in the sediment-laden river is calculated based on the discharge coefficient from the hydraulic manual or clean water model test. The method is suitable for the river with less sand. However, to the sediment-laden river, the change of muddy water’s physical characteristics induced by the sediment has a great effect on discharge capacity. As a widely applied weir in the sediment-laden river, WES practical weir’s discharge capacity directly influences the hydraulic structures’ layout form, flood-releasing scheme, and engineering safety. In this paper, a new three-dimensional electromagnetic current meter was put forward to be used in the model test of a rectangular water tank of 0.4 m wide and 30 m long. The muddy water with various sediment concentrations flowing over the WES weir was made by adding the sediment with a particle diameter of 0.027 mm, and the relevant hydraulic parameters were measured systematically. It was shown that, when the value of sediment concentration was less than 100 kg/m³, the composite discharge coefficient had no distinct correlation with the sediment concentration. When the value of sediment concentration was between 100 and 400 kg/m³, the composite discharge coefficient decreased with the increase of the sediment concentration. When the value of sediment concentration was greater than 400 kg/m³, the composite discharge coefficient increased with the increase of the sediment concentration. Based on the results of a series of model experiments and the natural river’s data analyses, the deviation effect from sediment concentration on WES practical weir’s discharge coefficient was demonstrated from the point of sediment-laden flow structure and motion mechanism, and the deviation modification of the weir flow’s discharge coefficient was stated under the condition of the sediment-laden flow. The calculation formulas of WES weir’s discharge capacity, which is available for different values of sediment concentration, were put forward with the method of dimension and correlation analyses, and the results were verified and corrected through the engineering observation data. The research results in this paper play an important role in the fundamental research of hydraulics and the construction of river regulation. The study not only provides a better calculation method of discharge capacity for WES weir but also has important academic and practical value for making sure the discharge capacity of hydraulic structures in the sediment-laden river.