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Prediction of the Unsteady Transition Behavior in Low Pressure Turbine Flows Using Time and Frequency Domain Methods


 The transient transition behavior of a two-stage low pressure turbine rig facility is investigated in terms of numerical studies. The surface of a second stage stator vane is equipped with a thin film sensor array along its suction side providing time-resolved measurement data of the underlying boundary layer. The measurement data indicate a laminar behavior over the accelerated region of the stator vane. At the decelerated region close to the vane’s trailing edge, alternating transition mechanisms of both bypass and separation induced transition combined with subsequent reattachment can be observed. The measurement data in combination with numerical results from a time-marching full-wheel simulation are used to assess the results from an unsteady flow simulation based on the harmonic balance approach in the frequency domain. For both time and frequency domain simulations, the turbulence behavior is considered by application of Wilcox’ k–ω two equation model in combination with Menter and Langtrys γ-Reθ transition model. The numerical results regarding transient distributions of intermittency and associated shape factor of the boundary layer are compared with proper measurement quantities in order to evaluate the capability of the applied harmonic balance solver to predict the unsteady transition behavior over the investigated vane’s suction side.