Computational analysis of the tip-gap flow of an axial ring fan

This research is focused on the study of the aerodynamic simulation of the flow recirculating through the tip-gap of an axial ring fans normally used in cooling systems of automotive engines. The aerodynamic discomfort behaves like a mechanism that generates acoustic roughness with highly significant effects; so, right out of that generated by the impact of the wake downstream of the rotor on the stator blades, it is one of the most important sources of noise at low frequencies, able to provide tonal and broadband contributions in the spectrum of SPL. This study is developed with a three-dimensional numerical modelling of an axial fan for automotive use through the application of fluid dynamics computational methods CFD. The three-dimensional modelling includes an unstructured grid and a turbulence's modelling based on RANS (Reynolds averaged Navier-Stokes) systems; thanks the commercial code called Star-CCM+ (CD-Adapco) it is possible to solve all the Navier-Stokes equations. Particularly, this study arises in continuity with the sperimental activity done in the aeroacoustic laboratory of DIME whose it is a deepening about aerodynamic deterministic phenomena involved. In fact the geometries reflect those used in the sperimental activity. The aim of this study is deepen the knowledge about the characteristics of the recirculation flow and its interactions with the flow normally evolving in the rotor. In particular the intention is pay attention to the genesis and the following evolution of turbulent structures of large scale which can generate tonal noise when meet the rotor blades.