CFD based Assessment of Fish-Friendliness of the Time Dependent Flow Field in a Kaplan Runner

A new major step in the application of CFD to the analysis of the pressure field in a Kaplan turbine is the simulation of the unsteady pressure field as presented in this paper. The time dependent interaction of guide vanes, runner and draft tube is predicted by means of an unsteady coupled CFD simulation. The resulting flow field is analysed with respect to both machine performance and possible effects on fish response. The paper discusses the effect of overhanging guide vanes on the velocity gradients and the respective shear stress as well as the pressure pulsations caused by the non-symmetrical draft tube inlet. The flow field resulting from the time dependent flow simulation is compared to the steady state flow simulation with respect to fish survival criteria. To complete the assessment of fish friendliness blade strike models are compared to CFD particle tracking methods.