Open Fan Noise Confinement Effects in a Closed Wind-Tunnel: Numerical Methodology and Evaluation

This work investigates, through numerical simulations, the acoustic confinement effects of an open fan test bench installed in a wind-tunnel with closed test section. The present activity makes use of the full IBM methodology developed in previous work, which consists in computing with a CAA solver, the propagation of the acoustic waves generated by an Open Fan acoustic source model injected in the CAA domain, in the presence of complex geometries and a realistic non-uniform mean flow previously obtained with a CFD solver. The CAA solver uses the Immersed Boundary Method (IBM) to deal with the bench and wind-tunnel geometries, which greatly simplifies the grid generation process and also drastically reduces the overall computational time by maximizing the explicit time step while propagating acoustic wave over long distances. Two simulations are performed for an operating point corresponding to the take-off condition: a free-field and a confined configuration with rigid walls. Despite strong reflected waves from the wind-tunnel walls, the free-field directivity can still be directly retrieved for the main directions of radiation.