Computational Fluid Dynamics
Universität Stuttgart
Institut für Strömungsmechanik Hydraulische Strömungsmaschinen (IHS)
The energy suppliers move their focus from nuclear and fossil-fuel energy towards the installation of renewable energy. Small hydro power plants are installed in yet unused dames and weirs as a result of promotions given by the European Union and the regulations of the Water Framework Directive to contribute to the energy transition in Europe. Axial turbines are typically installed at these locations. The focus of the project is the investigation of the influence of the gap flow respectively the gap size on the performance of the turbine and the effects on the flow field in the draft tube. The analysis is carried out for several different operating points with fully transient simulations of an entire axial propeller using hybrid RANS-LES turbulence models like SAS, SDES, and SBES. These turbulence models are able to resolve the developing vorticities in the runner gap and in the draft tube within sufficient fine computational grids. The numerical results can be validated with extensive experimental results which are performed in the laboratory of the Institute. The experiment provides accurate measurements of integral quantities, profiles of the axial and tangential velocity component at several positions in the draft tube and dynamic pressure signals at selected locations of the draft tube. The same gap widths are analyzed in the experiment and the numerical study.