Modeling flows in low-pressure turbine cascades at very low Reynolds numbers

This paper presents how transitional flows occurring inside low-pressure turbine cascades can be successfully simulated within a RANS framework. In particular, the emphasis will be put on cascades designed to operate at very low Reynolds numbers. Since such flows are difficult to model, a three-equation model Pacciani et al. (J Turbomach 133(3):031016, 2011), using the concept of laminar kinetic energy has been implemented into DLR in-house turbomachinery specific CFD code TRACE. The detailed implementation of the model and the first results are presented in this paper. The new model has been validated on the T106C turbine cascade. Like in the publication of Pacciani et al, short, long and open separation bubbles are well reproduced. A further assessment of the capability of the model has been carried out: two industrial relevant cascades have been computed. The first blade is an aft-loaded profile while the second blade is a front-loaded profile. For both design types, the agreement between the experiments and the computations is good at low Reynolds number. Notably, the long separation bubble found on the aft-loaded blade is well reproduced. At high values of the Reynolds number, discrepancies occur and are discussed.