Evaluation of OpenFOAM for CFD of turbulent flow in water turbines

Paper i proceeding, 2006

The purpose of this study is to evaluate the newly distributed OpenFOAM (www.openfoam.org) OpenSource CFD tool for turbulent flow in water turbines. The aim is to validate the OpenFOAM results for cases that have also been computed with other CFD codes, as well as have been experimentally investigated. Comparisons are made both with numerical and experimental results. The first case studied is the steady flow in the Hölleforsen (Turbine-99) draft tube. The OpenFOAM result proved to be comparable with results from all the major CFD tools on the market according to the proceedings from the Turbine-99 III workshop in December 2005 (www.turbine-99.org). An unsteady computation of the flow in the same draft tube has also been made, yielding an unsteady vortex rope with a period of 0.48s. All OpenFOAM draft tube results are similar to results obtained with CFX-5, and the results are close to the experimental results. The second case studied is the steady flow in the Hölleforsen runner. The computations have been performed both for a single runner blade passage using periodic boundaries, and for the full runner, yielding the same results. In all cases the tip clearance has been included and computations both with and without the runner blade clearance at the hub has been made. The computational results compare well with the experimental results. All the computations use wall-function grids and turbulence is modelled using the standard k-epsilon model.