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Acoustics comfort is a key point for the ground transportation market and in particular in the automotive area. A significant contributor to the noise levels in the cabin in the range 200Hz to 3000Hz is the HVAC (Heating, Ventilating, and Air Conditioning) system, consisting of sub-systems such as the air intake duct, thermal mixing unit, blower, ducts, and outlet vents. The noise produced by an HVAC system is mainly due to aeroacoustics mechanisms related to the flow fluctuations induced by the blower rotation. The structure borne noise related to the surface induced vibrations and to the noise transmission through the dash or plastic panels may also contribute but is not considered in this study. This study presents a digital approach for HVAC aeroacoustics noise predictions related to the ducts and outlet vents. In order to validate the numerical method flow and acoustics measurements are performed on production HVAC systems placed in an anechoic room.

A computational approach to evaluate rear-view mirror performance on wind noise in cars is presented in this paper. As a comfort metric at high speeds, wind noise needs to be addressed, for it dominates interior noise at mid-high frequencies. The impetus on rear-view mirror design arises from its crucial role in the flow field and the resulting pressure fluctuations on the greenhouse panels. The motivation to adopt a computational approach arises from the need to evaluate mirror designs early in vehicle design process and thus in conjunction with different vehicle shapes. The current study uses a Lattice Boltzmann method (LBM) based computational fluid dynamics(CFD) solver to predict the transient flow field and a statistical energy analysis(SEA) solver to predict interior noise contribution from the greenhouse panels. The accuracy of this computational procedure has been validated and published in the past.