3D numerical optimisation of an asymmetric orifice in the surge tank of a high head power plant
In this presented work, the results of 3D numerical investigations will be utilized to improve the 1Dnumerical calculation of water hammer and surge tanks of high head power plants. Usually, tabular values are used to quantify local head losses as a first approach. For existing high head power plants, the coefficients can be calibrated based on measurements. In a planning stage, physical laboratory tests and 3D numerical simulations provide an alternative to assess loss quantities. In case of the presented work, a 3D simulation using ANSYS CFX is carried out to calculate the local head loss coefficients. Furthermore, the investigated orifice is optimised for stationary and non stationary cases. The present investigations on an asymmetric orifice, which is located in an elbow and part of a restricted entry surge tank, have shown that the local loss coefficient for the numerical simulations is higher than the simplified theoretic approach (tabular value) The findings using a 3D numerical approach are in agreement with earlier laboratory experiments. Thus, the numerical method was applied to optimise the orifice geometry with respect to the asymmetric effects of the orifice and to minimise the construction costs.