Unsteady behavior of corner separation in a compressor cascade: Large eddy simulation and experimental study

Abstract

The present study carried out a pure large eddy simulation (LES) on a NACA65 linear compressor cascade (chord-based Reynolds number: 382 000), at an incidence angle of 4°. In this configuration, a corner separation at the juncture of the blade suction side and the end-wall is clearly observed experimentally. For the simulation, 852 CPUs are used in parallel and particular attention is paid to the inflow conditions, coupling LES with the calculation of the inlet boundary layer and associated velocity fluctuations. The shear-improved Smagorinsky model, which has been proved to be competent for turbomachines, is used in this study. Numerical results are carefully compared with pressure measurements, two-dimensional and stereo particle image velocimetry. LES is found to be superior to Reynolds-averaged Navier–Stokes approach in predicting the three-dimensional separated flows in the compressor cascade since pressure coefficients and losses are in very good agreement with the experiment. LES has been proven to simulate also the unsteady behavior of the separation. Finally, the experimental and numerical analysis of the inflow angle reveals high fluctuations of incidence upstream the leading edge of the blade near the end-wall, mostly associated with the incoming wall boundary layer.