Hydraulics of river flow and sediment transport parameters in case of unsteady water movement in the lower reaches of hydroelectric facilities on navigable rivers

The paper presents numerical experiments to evaluate the hydraulic characteristics of river flow and sediment transport parameters in the lower reaches of hydroelectric power plants on large navigable rivers. The results obtained made it possible to study the features of sediment movement in an unsteady water flow and develop certain recommendations for establishing boundary conditions when modeling channel transformations. The main conclusions obtained from the materials of numerical experiments are as follows: with the unsteady movement of water in the downstream of the hydroelectric power plant, sediment transport is activated, both in the summer observation period and in winter; the greatest discrepancies between hourly and daily average data are observed in the reservoirs located in the immediate vicinity of the hydroelectric power plant; the degree of increase in sediment consumption during the unsteady movement of water in the downstream of the hydroelectric power plant depends on the uneven regulation of water flow, the removal of the calculated hydraulic solution from the dam gate and the nature of changes in water content during navigation; in the immediate vicinity of the hydroelectric power plant, the intensity of sediment transport in winter becomes significantly less than in summer, as it moves away from the hydroelectric power station. The difference is decreasing; along the length of the river, as you move away from the waterworks, the intensity of sediment transport decreases. To test the results of numerical modeling, experiments were performed in a hydraulic tray. The obtained data are in qualitative agreement with the results of numerical experiments. During the experiments, it was found that the applied sediment consumption formulas show an overestimation of the calculated data compared with the measurement results.