In the present paper direct numerical simulation data of a low pressure turbine is investigated in light of turbulence modelling. Many compressible turbulence models use Favre average transport equations of the conservative variables and turbulent kinetic energy along with other modelling equation. First a general discussion on the turbulence modelling error propagation prescribed by transport equations is presented, leading to the terms that are considered to be of interest for turbulence model improvement. In order to give turbulence modellers means of validating their models the terms appearing in the Favre averaged momentum equations are presented along pitchwise profiles at three axial position. These three positions have been chosen such that they represent regions with different flow characteristics.
General trends indicate that terms related with thermodynamic fluctuations and Favre fluctuations are small and can be neglected for most of the flow field. The largest errors arise close to the trailing edge region where vortex shedding occurs. Finally, linear models and the scope for their improvement are discussed. Using locally optimized turbulence viscosities, the improvement potential of state of the art models is shown. On the other hand this study also highlights the danger of pure local optimization.
