14th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
The flow in a turbine stage is highly three-dimensional and unsteady due to the interaction of stationary stator and moving rotor. This situation poses a high challenge for the correct prediction of turbulence in a RANS simulation. The task is aggravated by the little available data of turbulence in a turbine stage at realistic flow conditions. At Graz University of Technology the flow through a transonic turbine stage was extensively investigated in the past using laser Doppler anemometry. At different measurement planes the velocities as well as turbulent fluctuations were measured. Based on this experimental data the turbulent inlet boundary conditions, which lead to the best agreement with the measurement data, were found in an unsteady CFD study. A very high inlet turbulence intensity had to be prescribed to meet the free-flow turbulence in the stage. Using these boundary values for turbulence, the unsteady flow in the stage was simulated and carefully analysed. The time variations of the flow are intensively discussed and compared with measurement data. Special emphasis is laid on secondary flow phenomena and turbulence generation.