Author(s): Stefan Walder; Peter Rutschmann
Linked Author(s): Peter Rutschmann
Keywords: Hybrid modeling; Intake; Vortex formation
Abstract: In this contribution the advantages of the combination of physical model tests and numerical calculations for the hydraulic optimization of an intake are shown. The Hydraulic Engineering Unit (IWI) was contracted to investigate the intake of the Kops reservoir of the new power plant Kops 2, optimizing design and susceptibility to vortex formation. Additionally to a physical model test, three-dimensional, numerical calculations were carried out to compare the results with laboratory measurements. The contribution focuses on vortex formation in the intake. The analyzed loading case for this contribution is not an operating condition. The possibility of different vortex classification is shown in generally. The danger for vortex formation is judged by a novel approach developed in a diploma thesis. The idea of this approach was to replace the qualitative and very subjective classification of flows according to HECKER (1981) with a quantitative criterion for which the mathematical definition of vorticity was used. By using results from numerical simulations a correlation between vortex type, relative submersion height and vorticity was established for a synthetic vortex generator. The original intake design and a hydraulically optimized design variation of the intake were analyzed for vortex formation in the physical model as well as in the numerical model. The numerical data were used to realize a vortex classification with the help of the new approach shown in this contribution. The mathematically defined function of the vorticity can either be obtained by numerical computations or by measuring the velocity distribution in a small scaled physical model. Together with the novel approach presented in this paper it will thus be possible to judge prototype vortex strength even in small scaled hydraulic models where surface tension effects prevent air-entraining vortices.