Numerical Analysis of Three-Dimensional Corner Separation in a Linear Compressor Cascade

(1)Laboratoire de Mecanique des Fluides et d’Acoustique, Ecole Centrale de Lyo´ n, 69130 Ecully, France(2)School of Jet Propulsion, Beijing University of Aeronautics and Astronautics, 100191 Beijing, China∗ Feng.Gao@ec-lyon.frABSTRACTNowadays, the internal flow in aircraft engine compressorscan be quite accurately reproduced at design condition by theCFD tools. However, CFD generally fails to simulate some sin-gular 3D phenomena, near off-design conditions, such as thecorner separation. Studies have pointed out that the separationregions are often over-estimated when the flow state is far fromdesign condition, owing to the turbulence model. Much workis devoted to improving the capability of the turbulence modelin capturing the onset and the extent of the corner separation,which is desired in the designing procedures.In this paper, steady RANS simulations are carried out in thesame configuration as an experiment of Ma et al. These simula-tions are obtained with a high-precision in-house Navier-Stokessolver (Turb’Flow). With the same mesh, an unsteady simulation(URANS) is subsequently presented, in order to investigate theinfluence of a fluctuating inflow.Attention is focused on a specific angle of attack of 4 de-grees, for which the three-dimensional corner separation isclearly observed. For the unsteady simulation, unsteadiness isimposed through perturbations of the angle of attack at the inlet.The results ofthe steady andunsteadycomputationsareanalyzedand compared with those of the experiment. The time-averagedURANS results agree well with the RANS results. The fluctuati nginflow does not show much influence on the mean performanceof the compressor cascade. The onset of the corner separationoccurs earlier in the simulations than in the experiment, consid-ering the blade surface pressure and the passage velocity pro-files. However, the cross-stream extent of the corner separationappears slightly under-estimated by CFD, according to the out-let total pressure losses andthe passagevelocityprofiles. Finally,the URANS simulation allows to recover bi-modal PDFs, as ob-served in the experiment.NOMENCLATUREc Chord lengthc

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