Unsteady flow simulation in hydraulic machinery

In the field of hydraulic machinery Computational Fluid Dynamics (CFD) is routinely used today in research and development as well as in the daily design phase. Today in industry mostly steady state simulations are applied. In this paper, however, an overview of unsteady simulations is shown for different applications. The presented examples contain problems with self excited unsteadiness, vortex rope in the draft tube, as well as applications with externally forced unsteadiness by changing or moving geometries and rotor-stator interactions. For the shown applications the requirements, potential and limitations of unsteady flow analysis are assessed.