Abstract
The flow in a transonic turbine stage still poses a high challenge for the correct prediction of turbulence using an eddy viscosity model. Therefore, an unsteady RANS simulation with the k-ω SST model, based on a preceding study of turbulence inlet conditions, was performed to see if this can improve the quality of the flow and turbulence prediction of an experimentally investigated turbine flow. Unsteady Q3D results showed that none of the different turbulence boundary conditions could predict the free-stream turbulence level and the maximum values correctly. Luckily, the influence of the boundary conditions on the velocity field proved to be small. The qualitative prediction of the complex secondary flows is good, but there is lacking agreement in the prediction of turbulence generation and destruction.
Highlights
Unsteady Simulation of a Transonic CFD codes are already highly developed and able to predict the flow even through very complex geometries, still assumptions and simplifications are necessary concerning turbulence
The computations were performed with the Navier–Stokes code LINARS, developed at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) by Pecnik et al [4], which has been successfully utilized for the solution of numerous applications
An unsteady flow simulation of a transonic turbine stage was performed in order to study if an unsteady simulation can give a better agreement with the measurement data than steady simulations done in the past
Summary
CFD codes are already highly developed and able to predict the flow even through very complex geometries, still assumptions and simplifications are necessary concerning turbulence. In this work, based on [6], a further attempt with an unsteady simulation of the transonic stage flow using the k-ω SST model is presented where particular attention was paid to the comparison of the measured turbulence after the rotor with the predicted one. This shall help to clarify the limitations of RANS simulations in predicting turbulence in highly loaded transonic turbine stages.
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