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Numerical simulations are performed to investigate noise generated by flow in automotive HVAC ducts. A hybrid computational method for analyzing flow noise is applied: Large Eddy Simulation (LES) for predicting flow fields and Multi-domain boundary element method for predicting acoustic propagation. LES gives time-resolved solutions of flow velocity and pressure fields. By applying the acoustic analogy theory, the unsteady flow parameters are translated into sound source in evaluating the acoustic propagation. The computational result shows the noise caused by the HVAC ducts is strong. The noise is of broadband with a peak value at 370Hz. A major contribution of the noise generation is from the center ducts. Two design modifications of the center ducts are explored to regulate the flow structures with the ducts for reducing noise generation. Test results demonstrate the effectiveness of the modifications.

Due to the energy crisis, one of the important challenges in the Auto industry is to reduce the fuel consumption of the vehicle. And the higher speed is, the more fuel consumption is taken by the aerodynamic drag. Mostly, the aerodynamic drag lies on the shape of the vehicle. Consequently, the improvement of the aerodynamics of vehicle shape, more precisely the reduction of their aerodynamic drag, becomes one of the main topics of the automotive researchers. For a container-truck, the three dimensions of the container are standard and unchanged, and the shape of cab is almost fixed by the aesthetic sculpt. For those container-trucks, aerodynamic additional equipments can decrease the aerodynamic drag evidently, especially the wind deflector. Accordingly, this paper describes a method which combines CAD, CFD, Approximate model and optimization carried out on the aerodynamic shape of a container-truck's wind deflector.