Abstract
Most criteria for the evaluation of velocity distributions (VD) in front of turbines in river power plants are derived for the section of the trash rack. Hence, an optimization of the approaching flow behind this section cannot be evaluated. The paper shows the adaption of the existing and well know Fisher & Franke (F&F) criterion, which was published in 1987. As a first step, different theoretical VD in pipes are used to illustrate the need of the modification. Furthermore, simplified obstacles in front of the turbine are analyzed with 3D-numerical simulations (ANSYS-CFX), where the results can help to compare realistic VD with theoretical obstacles. Still, within a next step the influence on the energy production should be investigated. This 1: 4 scale model test of a fully functional turbine in the laboratory is currently under investigation. With the help of this scale model test the adapted criterion should be evaluated.