Numerical prediction of clocking angle variations in a low-pressure turbine

The exact prediction of clocking angle effects is important for the aerodynamic and aeroelastic design of turbomachinery. Predicting accurately the wake propagation, wake-boundary-layer interaction, and potential field effect remains a challenge for eddy-viscosity-based turbulence-models and transition-models, even with (U)RANS. Therefore, this paper investigates the sensitivities of the prediction towards boundary conditions. The test case is the T106A low-pressure turbine cascade with upstream and downstream moving bars. This includes different inlet turbulence intensities and clocking angles. The influence of simplifications such as modeling the fully 3D (F3D) flow as a quasi 3D flow (Q3D) combined with a linear distribution of an axial velocity density ratio (AVDR) in axial direction will be demonstrated. The k-wSST turbulence model combined with the g - Req transition model is used. Special emphasis will be put on the analysis of the suction side boundary-layer, its separation, and transitional behavior. The numerical results are compared to the experimental data of the cascade test-case. Current results indicate that Q3D models with linear approximations of AVDR effects struggle to predict the influence of the clocking angle variation on the flow. While the potential field effect from the downstream bars is well predicted with Q3D simulations, the authors show that Q3D simulations combined with the choice of AVDR influence the dynamics of the boundary-layer. Furthermore, it will be shown that the interaction between wake and boundary-layer, as well as the development of the boundary-layer are not predicted well by the current (U)RANS model for both F3D and Q3D. This requires more attention in future work.