CPU-Efficient Acoustic Design for Axial Fans

Low noise design of ventilation systems is an emerging topic in modern vehicle industry, since the thermal and acoustic comfort experienced by the passenger is even more important to define design criteria of HVAC components. Despite of the recent progresses of numerical approaches in the frame of aerodynamic and aeroacoustic simulation, the state of the art in Computational Fluid Dynamics (CFD) and Computational Aeroacoustics (CAA) is still far away to be capable to drive the design of low-noise targeted components. This is mainly due to the high complexity of physical phenomena involved in the noise generation mechanisms, mostly related to flow turbulence usually requiring approaches (e.g. Large Eddy Simulation, LES) with computational demands that cannot be easily afforded for industrial design purposes. The goal of this paper is providing an inexpensive, fast and reliable technique for the aeroacoustic simulation of broadband noise arising from axial fans. It is based on the acoustic semi-empirical model of Brooks et al. (NASA, 1989) coupled with a simplified aerodynamic model for rotor applications based on the Blade Element Theory (BET). The proposed technique, able to distinguish between noise sources arising from turbulent eddies, large vorticity and laminar instabilities, is validated on the experimental data available from literature (Carolus et al. 2007) for an axial fan. The good agreement between experimental and computed SPL together with the huge potentialities offered in terms of noise sources identification and breakdown make this approach suitable for industrial fan design and optimization