The overall noise level in a vehicle cabin has been improved constantly over recent years, bringing previously masked acoustic sources like automotive heating, ventilation and air conditioning (HVAC) systems into the focus of acoustic optimization. Moreover, with the increased airflow performance of modern HVAC systems, noise emissions are more likely to occur. As a result, acoustic comfort is now treated as equally important to customer's satisfaction as thermal comfort. The awareness on the manufacturers' side about acoustic comfort lead to the objective of enabling reliable predictions of noise emissions from air distribution systems in the early development phase. This paper starts with an overview about the basics of aeroacoustic theory as well as the possibilities and limitations of numerical simulation. Flows in air handling systems of vehicles are characterized by low Mach numbers and high Reynolds numbers. For these conditions a hybrid simulation method has shown to be highly promising in terms of effort versus accuracy. This methodology subdivides the aeroacoustic problem into two parts; sound generation and sound propagation. The computation of sound generation is done by the computational fluid dynamics (CFD) solver FLUENT, using a time dependent large eddy simulation (LES) approach. The results from the CFD simulation were used to determine source terms for an inhomogeneous wave equation for sound propagation based on an aeroacoustic analogy. The wave equation was solved with a Boundary-Element-Method (BEM). The hybrid computational aeroacoustics (CAA) method was used on a straight duct flow; the influence of different simulation parameters was discussed. Subsequently, results for the sound pressure level spectrum of an automotive HVAC unit and a register are presented and compared with measurements.
Recent developments in numerical aeroacoustics in the automotive industry
Neue Entwicklungen auf dem Gebiet der numerischen Aeroakustik in der Automobilindustrie
2005
16 Seiten, 15 Bilder, 2 Tabellen, 10 Quellen
Conference paper
English
Automotive aeroacoustics: An overview
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