No abstract

The system oscillations of a water power plant caused by the draft tube flow in part load are investigated. A coupled simulation of a one-dimensional water hammer analysis and a three-dimensional flow calculation of the draft tube vortex rope is applied. With this approach the excitations of the oscillations, frequencies and amplitudes, have not to be estimated but are obtained from the simulation. This allows an accurate prediction of the system oscillations caused by draft tube surge.

The vortex instability in a spherical pipe trifurcation is investigated by applying a Very Large Eddy Simulation (VLES). For this approach an new adaptive turbulence model based on an extended version of the k-ε model is used. Applying a classical Reynolds-averaged Navier-Stokes-Simulation with the standard k-ε model is not able to forecast the vortex instability. However the prescribed VLES method is capable to predict this flow phenomenon. The obtained results show a reasonable agreement with measurements in a model test.