March 6 - 8, 2017 | Berlin
LEADING ENGINEERING SIMULATION CONFERENCE
In this study the attention was focused on a secondary noise source of the vehicle such as the refrigerant system. The problem was initially described as an annoying whistle noise, which was clearly audible inside a vehicle cabin. The issue frequency identification through time-frequency plots showed a typical acoustic resonance occurring along the refrigerant gas duct, at a specific flow speed. This phenomenon was worsening significantly the sound quality of the vehicle interior noise.
Therefore, the aim of this work was to describe the whistle excitation and generation mechanism through STAR-CCM+® computational aeroacoustics and subsequently propose duct shape modifications for preventing the issue. Steady state analysis, combined with broadband source models (BNS), gave preliminary indications of possible noise sources areas in the refrigerant gas duct.
The effect of the acoustic field on the fluid dynamics and the flow field feedback mechanism was later studied with a Direct Noise Simulation (DNS) approach with a compressible DES simulation, to model flow noise sources and acoustic propagation at the same time. Furthermore, the STAR-CCM+ Acoustic Suppression Zone (ASZ) model allowed the prevention of unphysical waves reflections on the duct inlet/outlet boundaries. The spectral analysis on simulation results has shown a good resonance prediction and finally has confirmed the whistle avoidance in the new proposed ducts.