Substantiation of countervortex spillway structures of hydrotechnical facilities

The construction and reconstruction of waterworks sets a number of scientific and engineering tasks that require a new approach to their solution. One of the promising areas for solving these and a number of other problems is the use of swirling water flows in hydrotechnical facilities. The article presents the results of physical simulation of spillway counter-vortex systems. The model had a damping chamber diameter of 0.15 m and was tested at a head up to 8 mH2O and a flow rate up to 0.11 m3/s. As a result of the conducted experiments, the values of the flow coefficient of the entire system were obtained. The water-carrying capacity was determined for several modes of operation of the model by means of a combination of switching valves that brought water to the inlet nozzles of the model. In addition, a change in the mode of operation of the model was carried out by changing the vacuum in the near-vortex zone of the counter-vortex flow in a wide range.A self-similarity of the flow coefficient by the head and the Reynolds number has been established. The physical modelling has made it possible to formulate a well-grounded approach to the hydraulic calculation of counter-vortex spillway systems. One of the most important issues studied experimentally in the process of the described hydraulic tests was the determination of the energy damping capacity of counter-vortex spillways, reflecting their effectiveness. The energy damping capacity was determined by the energy damping factor, reduced to the general head in the model. The article presents the main schemes of local water flow swirlers for the formation of a counter-vortex flow, which can be used in hydrotechnical practice. Some of their geometric and hydraulic characteristics are considered. A simplified scheme of hydraulic calculation of a counter-vortex spillway structure for various types of swirlers and constructive solutions of a spillway system (an open type or an underground tunnel) is proposed. The authors compared the efficiency of the proposed method for damping the energy of the spillway flow and the hydraulic scheme with a sudden expansion of the flow according to the Borda formula. The counter-vortex method of damping the energy of the transit flow has a much higher efficiency in comparison with sudden expansion. The study suggests directions for further research on complex counter-vortex flows.

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