Abstract

The goal of this work is to predict the boundary layer transition induced by a separation bubble on the suction side of a turbine blade of a linear turbine cascade using Large Eddy Simulation (LES). The numerical simulations refer to the linear turbine cascade T106D-EIZ tested at the Institute for Jet Propulsion of the Bundeswehr University Munich (Germany). The blade pitch was increased compared to the design point in order to have a higher load and enhance the formation of a separation bubble at the suction side of the blade. Different flow configurations were tested and the transition of the boundary layer was evaluated. For the numerical case, the operating condition with an inlet turbulence below 1% was used. In the first part of this work, the LES setup is discussed. A modified Smagorinsky subgrid-scale model is used to reduce the turbulent viscosity in the region closest to the wall. The computational grid is designed according to the information coming from the Taylor and the Kolmogorov length scales. These parameters are found from RANS k-omega SST simulations. The fifth-order accurate WENO scheme was used for the computation of the cell fluxes. In the second part of the work, a comparison between the results of the LES simulations and of the RANS k–ω SST simulations with the γ–Reθ transition model is done. Integral and statistical parameters of the boundary layer from the simulations with the two models are evaluated and compared. The ability of the LES and the RANS models to predict the boundary layer evolution along the blade profile and the point of separation will be discussed.

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