LES and CDNS Investigation of T106C Low Pressure Turbine

Abstract

This paper investigates the aerodynamic performance of a low pressure turbine, namely the T106C, by large eddy simulation (LES) and coarse grid direct numerical simulation (CDNS) at a Reynolds number of 100,000. The existing experimental data is used to validate the results. The effects of sub-grid scale (SGS) models, mesh densities, computational domains and boundary conditions on the result are studied. A separation zone appears downstream 60% S/S0, which is difficult to be predicted precisely. Two SGS models, i.e. Smagorinsky and WALE model are implemented. WALE model produces a better result than Smagorinsky model when the mesh is coarse. For the fine mesh, the difference due to the SGS models becomes smaller. It is surprising to find that CDNS produces very similar results to WALE model, and their results are in better agreement with the experiment than that of Smagorinsky model. The computational domain is also important for the prediction of the flow near the midspan. 3D features of the separated flow have an effect on the downstream flows, especially for the area near the reattachment. Sufficient long spanwise computational domain is important for an accurate prediction. The current study also find that the endwall secondary flow has an effect on the flow separation near the middle span, which was seldom discussed before. By considering the effects of endwall secondary flows, better prediction of the flow separation near the blade midspan can be achieved. The effect of the endwall secondary flow on the blade suction side separation is also explained with the analytical method based on the Biot-Savart Law.