Suspension concentration distribution in a stream constructed by spur No. 19 on the Amu Darya river

Abstract

The concentration of suspended solids is the main indicator of the flow transporting suspended sediments. Knowing its value, it becomes possible to predict channel processes on rivers, the timing of sedimentation tanks and reservoirs. Establishing patterns of the influence of structures on the redistribution of liquid and solid runoff is also a priority task. The main goal of this work is to establish the regularities of the distribution of the concentration of suspended matter in a stream constrained by a transverse spur. The problem is considered for the second time using materials from field studies conducted on spur No. 19 in 2020 on the left bank of the Amu Darya river. The methodology of field studies remained the same as for the first time on dam No. 30 in 2019. The positions of the sections and verticals during sampling to determine the concentration of suspended matter were assigned based on the hydraulic structure of the constrained flow. Considering the presence of homogeneous zones of a weakly perturbed core, intense turbulent mixing and reverse currents, as is customary in the theory of turbulent jets with an admixture propagating in a confined space. On verticals, samples were taken at two points 0.2H and 0.8H, and at shallow depths at a depth of 0.6H. Field observations established that in the zone of the slightly disturbed core of the distribution of the concentration of suspended matter along the depth, it has the shape of a “boot”; however, the length of the toe is much shorter than that of the dam 30 and is observed only in the sections P-P and O-O, and in the other sections there is a leveling in depth. On other sections, they are close to logarithmic. The maximum concentration of suspended matter was observed in the section of confinement O-O at point 0.8H 7.66 kg / m3, which in the section of confinement under the influence of a new spur occurs deep and lateral erosion of the channel. The distribution in plan in the zone of a weakly disturbed core is close to uniform. Here again, in the zone of intense turbulent mixing, it obeys the theoretical Schlichting-Abramovich dependence for the initial section. With the help of the results obtained, it is possible to predict the siltation of the inter-dam space and the boundaries of the new coastline in the future.

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