Air flow phenomena in heating, ventilation and air conditioning (HVAC) units, ducts and vents are among the major noise sources limiting passenger comfort. BEHR has pioneered in applying computational fluid dynamics (CFD) simulation to identify flow induced noise sources with several research projects. The paper will focus on the results of two typical cases: The flow around a partially closed flap in an HVAC unit and the jet behind the grille of a vent, through which air is entering the cabin. The comparisons of measured and CFD-predicted noise spectra show good agreement at various inner surface locations. Accurate noise source prediction is essential for succeeding noise propagation calculations and comfort evaluations. With the work presented in this paper, BEHR has successfully established aeroacoustic CFD analysis, particularly the reproduction of aeroacoustic source regions in flows occurring typically in automotive AC (Air Conditioning) applications. Comparisons of measured and CFD-predicted power spectral densities of pressure fluctuations at various inner surface locations show good agreement. The vital choice of discretization schemes, solver options, turbulence modelling, meshing requirements, up front mesh quality analysis and many other crucial points have been addressed and thoroughly analysed. In addition, comprehensive experience has been gained in handling the extremely large data sets as well as in setting up monitoring and postprocessing schemes to analyse the results efficiently. For the time being, extensive use of these methods in industrial projects is limited by the extreme requirements in terms of computational resources and/or calculation time. The next step will be the addition of noise propagation analysis, based on the acoustic sources from the CFD region. This task includes the identification of the actual acoustic sources by correlation techniques, distinguishing between 'pseudo'-sound pressure fluctuations and the real sources of noise, which is propagated to the passenger ears. Another direction for future work is the extension of the application range to more complex cases like blowers and heat exchangers.
Aeroacoustic CFD simulation for automotive air conditioning applications: Behr's experience
Aeroakustische CFD-Simulation für die Kraftfahrzeugklimatisierung: Erfahrungen der Firma Behr
2007
9 Seiten, 8 Bilder, 7 Quellen
Conference paper
English
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