Dynamic orifice model on waterhammer analysis of high or medium heads of small hydropower schemes

The most severe hydropower transients are induced in long hydraulic circuit s due to extreme operating conditions. A computational model was developed in order to on one hand ensure waterhammer system control and, on the other hand, provide a more reliable and easier analysis for different specific s peed turbines and alternative solutions of the system as a whole, through i nteraction between different hydraulic components. In reaction turbines, ru naway conditions and guide vane closure cause significant discharge variati ons and pressure fluctuations that can affect the design of conveyance syst ems. A new approach for groups modelling as dynamic orifices concept was de veloped enabling the characterisation of the integrated system. The simulat ion results were compared with laboratory tests. This model can be used in the initial stages of civil works design as an efficient way to better char acterise the hydrodynamic behaviour of the system when equipped with reacti on turbines.