Some Experiences About the RANS Modeling of UHBR Fan: The Case of ECL5/CATANA

With the advancement of modern fan architectures, dedicated experimental benchmarks are becoming fundamental to improve the knowledge of flow physics, to validate novel CFD methods, and to fine-tune existing methods. In this context the open-test-case ECL5/CATANA, representative of a modern Ultra High Bypass Ratio (UHBR) architecture, has been designed and experimentally investigated at the École Centrale de Lyon (ECL) on a novel test facility with multi-physical instrumentation, providing a large database of high quality aerodynamic and aeromechanic measurements. In this paper, a thorough numerical study of the fan stage aerodynamics has been performed using the CFD TRAF code developed at the University of Florence. The fan stage performance has been studied at design speed over the entire operating range. Results have been discussed and compared with datasets provided by ECL. A detailed sensitivity on numerical schemes and state-of-the-art turbulence/transition models allowed the selection of the best numerical setup to face UHBR fan simulations. Moreover, to have a deeper understanding of the fan stall margin, unsteady simulations have also been carried out. The results showed the appearance of a blade tip instability, precursor of a rotating stall condition, that may generate non-synchronous blade vibration.