Aeroacoustic Analysis of a Low-Subsonic Axial Fan

Abstract

A mesh convergence study of direct aero-acoustic simulations of a typical automotive engine cooling rotor is performed. The simulations are performed using the Lattice Boltzmann Method (LBM) that has been extensively used in the recent years for low speed fan applications. The influence of the mesh refinement on the global performances, the pressure distribution over the blade and in the wake and tip gap zones is investigated using the large experimental database available. The direct acoustic predictions for the different numerical setups is compared with acoustic measurements and a Ffowcs Williams and Hawking’s analogy is applied to identify the noise source contributions from the rotor parts. With the three setups investigated the convergence is achieved on the global performances and the sound power spectra. Still some discrepancies between the setups appear in the unsteady pressure loading of the blades and the wake flow. The blades are seen as the main noise contributors particularly the cusp region near the hub and the tip region with the tip flow recirculation.