Abstract Simulation of unsteady flow of SF6 gas in a simplified high-voltage circuit breaker model describing the nozzle, contacts and their nearest surrounding is presented. SF6 is considered as viscous, compressible, real gas described by Redlich-Kwong model. Heat transfer is taken into account due to the gas compressibility. The heat source, triggered by the electric arc between the contacts, was out of the scope of the current research, thus it was not included in the simulations presented. Turbulence, caused by the gas viscosity, is described using realizable k-ε model. In the simulation model, one of the contact sides – electrodes, is considered as moving at prescribed velocity. The part of the space ‘swept’ by the moving electrode is considered as the gas with imposed artificially increased viscosity in order to imitate the rigid body behaviour. Thus, no moving parts of the computational mesh are used in the model. The conservation equations of mass, momentum and energy, given in integral form, are solved using a finite-volume method on unstructured computational grids.
Paper accepted: 27.05.2019. Preliminary Notes SUMMARY In this paper, a model based on numerical solution of two ordinary differential equations is used to obtain the water level in the surge tank and the static pressure in the headrace tunnel – the properties of essential importance for the functioning of the water supply system during the turbine shut-off. The model allows a fast and reliable simulation of the hydraulic processes in the headrace tunnel and the surge tank. It was validated by comparing the numerical results with the data available from the experiments conducted under real conditions in a surge tank of the HPP Jablanica. This model is used to analyze of influence of different parameters on variations of water level oscillation in the surge tank and the static pressure in the headrace tunnel.
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