Regulation of the flow in the area of the damless water intake

Abstract

The article discusses the results of numerical studies of the flow of the Amudarya river above the point of the damless water intake to the head structure of the damless water intake to the Karshi Main Canal-KMC. The system of two-dimensional equations of hydrodynamics-Saint-Venant is used as the basis of the mathematical model. In this work, a series of calculations of the field of currents in the river channel during low-water periods is carried out. Below are the main research results and proposals for ensuring the stable operation of the damless water intake in low-water conditions. The applicability of a numerical model composed of the equations of shallow water -the vector equation for the conservation of momentum and the scalar equation for the conservation of mass, has been proved, when describing a flow with the presence of circulation zones, which is typical when the water flow is constrained by blind dams. In this case, the solution pulsates around a certain average value, and the average length of the circulation zone behind the sudden expansion of the open flow is in good agreement with laboratory experiments. Numerical studies have shown that the device of a jet-guiding dam 150 m above the water intake gate in the CMC is more effective than when the dam is located 250 m above. In essence, dam № 2 with a length of 65 m does not affect the conditions at the water intake in the KMC at all, and dam № 2 with a length of 120 m is almost equivalent in its impact on the flow to dam №1 with a length of 50 m. Analysis of the results shows that the placement of an additional threshold in the Amudarya river bed improves the situation by raising the water level at the water intake. The threshold is flooded even at low water levels, which reduces the speed load on its body. At the same time, the threshold is located directly at the beginning of the channel, in part to protect the intake from incoming sediment, and high enough speed water glistening over the threshold in line, ensure the transit of sediment that can reduce enters the intake. Such measures will reduce the turbidity of water entering the channel. This, in turn, reduces the intensity of the silting process.

Increasing efficiency of flow energy damping with lateral water intake

“…When installing the model, the width of the tunnel tray was maintained using templates installed in pairs along its entire length [15][16][17][18][19][20][21][22].…”

“…However, under certain conditions, this space is either insufficient to accommodate the outlet channel or completely absent. Therefore a large amount of excavation has to be performed [10][11][12][13][14].…”

Calculation of planned flows taking into account deformations of bottom sediments in a dam-free water intake

“…Here, the main flow, depending on the current and approach, is reflected at an angle and directed to the opposite erosional bank, where the main stream forms a stall current causing erosion of the coastal area of the Kyzylaak Village. At the head section of KMС, in the earthen channel of the canal from the head water intake to the first pumping station, silting occurred due to insufficient volume of treatment work [18][19][20]. As a result, there was a rise in the bottom of the channel due to the residual volumes of silting, which has accumulated throughout the years.…”

Recommendations for the assessment and forecast of shore deformations in the average flow of the Amudarya river

“…Since one of the main reasons for the occurrence of intense erosion of the banks of the Amudarya River in the meanders is the stall of the flow, i.e. the formation of a stall current, based on long-term data of field studies of the river, in [20], the cause of the occurrence of a stall current is explained as follows. The analysis of the resulting stall current begins with a consideration of the specific features of the meandering course of the channel flow.…”