Numerical analysis of acoustic noise from an electronic cooling fan at flow disturbed by an external obstacle

Abstract

Axial cooling fans are widely used in data center dense Hard Disk Drive (HDD) storage systems. However, these fans emit high noise levels and degrade HDD performance at certain frequencies. Flow at the fan's inlet can be highly turbulent due to the wake generated by fan components such as struts, finger guards, stators/guide vanes, shrouds, and other external system components such as connectors and mounts, power cables and components, circuits etc. The wake-fan interaction also causes high tonal noise. Therefore a proper understanding of this noise mechanism will help optimize the cooling system in nextgeneration high-performance HDD enclosure systems. This paper focuses on studying this phenomenon using numerical simulations of a typical data center cooling fan combined with various simplified strut geometries as the obstacle. The high-fidelity Computational Fluid Dynamic (CFD) method, Large Eddy Simulation (LES), was used to obtain a transient flow field. The Ffowcs-Williams and Hawkings acoustic analogy was used to predict far-field noise.