Mateusz Hämmerling

The operation of water structures causes various problems. They are related, for example, to the material carried by the water, hydrological conditions, range of operation of hydroelectric turbines, or water elevations at the lower position of the hydroelectric power plant. Among the various operational problems, this article focuses mainly on the impact of the backwater of Gwda river on the water level elevations at the lower station of the Stary Młyn hydropower plant in Dobrzyca. The power plant is located on Głomia river. The analysis was carried out for different flow variants in both the Gwda and Głomia rivers. The effect of characteristic flows on the water surface level at the lower station of the hydropower plant was examined. It was found that the water surface level at the lower station of the hydropower plant is strongly influenced by flows higher than the average high flow on Gwda river. Due to the extent of the backwater in current operating conditions, the hydroelectric power plant is shut down from flows on Gwda river of 30–28 m3/s (flows that are not much higher than the multi-year average SSQ). The modeling results were confirmed by an analysis of power plant shutdowns of normal operation especially in wet years, when the plant did not operate for almost half of the year (188 days), with losses of 203 MWh. It was also shown that even a small additional damming of water, e.g., of the order of 0.2 m, can extend the operating time of a power plant up to 249 days even under unfavorable hydrological conditions. Factors related to climate change are beginning to play an increasingly important role in the current operating conditions of small lowland hydroelectric power plants. They can contribute to a reduction in electricity production. The proposed solution related to the possibility of greater water retention on dammed-up water barrages allows one to partially offset these problems as well.

Analysis of the results of the hydraulic calculations of a slotted separator, allowed for changes in the separator design taking into account the reduction of flow turbulence, ensuring the continuity of water flow and sediments as well as optimal location of the slots. The separator is an important element of the installation for hydromechanical removal of sediments from the bottom of a water reservoir. Tests were carried out on the physical and mathematical model. Hydraulic calculations and numerical simulations were carried out using the SSIIM (Simulation of sediment movements in water intakes with multiblock option) program. The program enables three-dimensional analysis of flows and transport of sediments in rivers and canals by solving the Navier-Stokes equation and the turbulent model k-. A number of numerical experiments of the separator work were carried out for various design solutions regarding the geometry of the inlet and outlet channels and their connection with the chambers as well as slots system. The numerical simulations and conducted research on a physical model, allowed to develop an optimal solution.