UNSTEADY FLOW SIMULATIONS OF AN AXIAL COMPRESSOR CASCADE SUBJECTED TO FREE STREAM WAKES

The flow through a 2.5D axial compressor cascade bladerow is simulated using a compressible Lattice-Boltzmann Method. The simulations are carried out for a nominal flow condition that yields a Reynolds number of 300,000 based on the axial chord and an inlet Mach number of 0.66. The simulations incorporate incoming wakes generated by moving bars with an equivalent reduced frequency of 1.9. A URANS simulation is carried out first, which reveals deficiencies in predicting time-averaged isentropic surface Mach numbers and wall shear stresses when compared against published DNS results. In order to increase the accuracy of the simulation, an implicit LES is run on a wall-resolved mesh. These results match the reference data because transition effects are correctly accounted for. A new, transition enabled hybrid RANS-LES approach is then carried out which shows that similar accuracy as the wall resolved LES can be obtained.