Numerical Investigation of Location and Coherence of Broadband Noise Sources for a Low Speed Axial HVAC Fan 2014-01-2054

In hybrid and electrical vehicles new challenges in meeting the drivers' expectation with regards to acoustic comfort arise. The absence of the internal combustion engine noise enhances the passengers' perception of other noise sources, such as the Heating, Ventilation and Air-Conditioning (HVAC) system. Therefore efficient and reliable numerical models able to predict flow-induced broadband noise have become a major research topic in automotive industry.

In this framework, the Zonal LES coupled with the Ffowcs Williams-Hawkings (FWH) acoustic analogy are capable to simulate broadband noise from low speed axial fan. As demonstrated in previous works from the authors, this approach is able to cope with the complexity of the physical phenomena involved (i.e. turbulent noise generation, laminar-to-turbulent transition, etc.), even though the numerical model requires a careful setup of the mesh topology, boundary conditions and simulation parameters. The aim of this article is to provide the scientific community with the latest developments of our research work on numerical modelling of broadband noise from axial fans, focusing on the performance of two different mesh topologies to locate and estimate the noise sources. The relation between the hydrodynamic pressure fluctuations on the blade and the acoustic pressure has been investigated, focusing on noise sources coherence for different ingested turbulence intensities.

The results of the numerical simulations are compared with the experimental data acquired by the authors.