The article is devoted to the study of the influence of the damless water intake on the hydraulic and alluvial regime of the river, the channel of which passes through easily washed out soils. The analysis of the dynamics of the river bed morphometry and hydraulic elements of the flow in the area of the damless water intake is carried out. As a result of the analysis of the data of long-term field studies and hydrometric measurements at the closest section to the damless water intake and in the area of the damless water intake of the Amudarya River, functional relationships were established between the morphometric parameters of the channel and the hydraulic parameters of the flow. The dynamics of the Shezi coefficient, hydraulic resistance, and the channel roughness coefficient in connection with the hydrodynamic characteristic of the flow are established.
This topic is the design characteristics of the liquid and solid runoff of the Amudarya river in the area of the hydroelectric complex, according to which the average long-term flow of the river at the site of the hydroelectric complex is 46.5 km3, the discharge is 1470 m3/s, the maximum is 5760 m3/s (July) and the minimum is 186 m3/s (March). The amount of suspended sediment reaches 5 – 6 kg/m3, and bottom 5 – 8% of suspended sediment. The annual volume of suspended sediment is 120 million tons, and taking into account bottom sediments – 130 million tons. It is noted that due to low water conditions, the Takhiatash dam operated with completely closed gates in all spans for a significant part of the year. The authors of the article provide data comparing the actual flow rates of turbidity and backwater at the Takhiatash hydroelectric complex with the calculated ones. It is proved that sharp fluctuations in the water level in front of the dam and water intake into the canals lead to a change in the hydraulic and alluvial operation of the canals. As shown by the analysis of the river channel cross-sections in the upper reach of the Takhiatash hydroelectric complex, in the initial period of operation, there is a decrease in the level of the river bed bottom. The subsequent years of operation of the hydroelectric complex (after 1982) were characterized by the stability of the ongoing channel processes in the downstream, which is characterized by its own level and discharge regime for each characteristic year. It is noted that the operating mode for dry years, which are characterized by the fact that during periods of chronic low water the gates of the shield dam are almost completely closed and its role in regulating the level regime is almost lost. In this case, the level and flow rates are regulated mainly by end regulators in the right-bank and left-bank systems of main canals, which in turn depend on the demands of limited water consumers. Under these conditions, it is extremely difficult to regulate the water level in the headwater, since it is required to keep at a certain level of the water level. It is noted that there were no difficulties with water intakes in high-water years, and the main difficulties are associated with the passage of flood flows through the shield dam. In recent years, there has been a rapid rise in the water level in the upstream, despite all the open gates of the dam, the navigable lock and water intake structures, which are explained by the influence of the introduced ponds on the throughput of the shield dam. It has been substantiated that without any damage to the water intake during the growing season, it is possible to effectively flush the headwater with a constant decrease in the water intake coefficient below the critical value of the water intake coefficient Kv < 0.55. In practice, for the Takhiatash hydroelectric complex, this means that the flushing flow rate should be at least Q ≥ 250 – 300 m3/s. Recommended: for the normal functioning of the Takhiatash hydroelectric complex, taking into account the requirements of all water consumers and sanitary passes to the downstream, it is necessary to clearly link with the operating regime of the Tuyamuyun reservoir.
A mathematical model is presented, a hydraulic jump that appears during the transition of the flow from a turbulent state (Fr>1.0) to critical (Fr<1.0). The main assumptions made to obtain the divergent form of the Saint-Venant hydrodynamic equations are given: - planned (two-dimensional) effects do not affect the flow (but still local energy losses due to sharp turns and changes in the channel shape in the plan can be taken into account; to take into account such losses in local sections of the channel increased local hydraulic resistance is introduced). The results of numerical studies of the downstream of the culvert structure of the medium-pressure reservoir are presented. The developed numerical model using explicit difference schemes is presented. Based on the results of numerical studies of the hydraulic jump, the possibility of establishing the degree of quenching of the excess flow energy having the destructive ability of the construction of the downstream of medium-pressure reservoirs is substantiated. The calculation results showed that an increase in the hydraulic resistance value promotes the displacement of the hydraulic jump against the current and an increase in its associated depths. At the concatenation site of the upstream, there was a sharp decrease in the Froude number from 2.76 to 0.69, with a change in average speed from 8.81 m/s to 3.26 m/s. It is substantiated that from the calculated values of the vertical dimensions of the hydraulic jump with various values of hydraulic resistance and the throughput of the structure, it is possible to determine the horizontal dimensions of the jump, which makes it possible to select the optimal sizes of the downstream attachment zone in and after the hydraulic jump.
The paper analyzes the dynamics of planned and deep deformations on the section of the Amudarya River in the area of the damless water intake in the main structure of the Karshi Main Canal-KMC. The results of field studies of the state of the canal situation of the Amudarya River at the site of a damless water intake are studied. The course of riverbed processes in the riverbed is studied. Recommendations for improving water intake conditions have been developed. According to the results of the field survey and the study of the head section of the supply canal, the state of the Amudarya riverbed in the water intake zone was assessed. The results of surveys of the hydraulic and pumping modes of sediments of the Amudarya River in the area of the damless water intake are analyzed and summarized. The results of field studies of the canal situation of the Amudarya River in the water intake area in the Amudarya River KMC in the area of the Karshi head water intake are studied. The riverbed situation is not characterized by constant hydraulic characteristics over time for the same water flow rate, i.e. with the same water horizon marks, the flow rates may differ from each other by about half, and with the same flow rates, the horizon marks may vary up to ± 0.6 m. This is explained by the extreme instability and high mobility of the canal, and large deformations of the canal occur in a short time. The hydraulic regime of the river is characterized by a significant redistribution of speeds, depth and width of the flow. The range of their changes is within: Maximum speed >Vmax =2…5 m/s; average speed Vav = 0.5…2.5 m/s; depth H max = 4…14 m, Hav = 1…5 m; width B = 300…2000 m; slope i = 0.00016…0.0003. It is established that the characteristic feature of the river is that at a constant flow can have different average velocities depth and width, for example, when Qw = 1000 m3/s, respectively, v = 0.6…1.7m/s, B = 180…1030m, Hav = 1.1…4.3m.
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