The viscous flow around a rotating axial fan at a Reynolds number of 9.36 × 10~5 based on the outer casing diameter is investigated by large-eddy simulation (LES) with special focus on the tip-leakage flow region. A massively parallelized finite-volume flow solver for compressible flows based on hierarchical Cartesian grids is used. The immersed boundaries of the fan geometry are handled by a fully conservative cut-cell method. A 72° segment, which includes one of the five fan blades, is resolved with approx. 250 million cells, for which a rotational periodic boundary condition for Cartesian meshes has been developed. Results of the instantaneous and the mean fan flow field are discussed and compared to Reynolds-averaged Navier-Stokes (RANS) results of a 360° simulation. The main differences are observed for the turbulent kinetic energy in the wake region generated by the tip-gap vortex. Furthermore, the influence of the tip-gap size on the vortical structures is investigated. It is shown that a reduction of the tip-gap size leads to a change of the shape and size of the tip-gap vortex. Additionally, more separation and counter-rotating vortices are generated inside the tip-gap, which, however, result in a lower turbulent kinetic energy.
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