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The aerodynamic optimization of passenger cars has become a major task in the development process of SVW when developing cars for the Chinese market. The pressure to reduce fuel consumption and emissions is leading to aggressive targets for aerodynamic drag. Furthermore, Chinese regulations require the publication of aerodynamic drag of vehicles sold in the Chinese market. This paper describes the approach taken by Shanghai Volkswagen (SVW) for the aerodynamic development of the New Lavida. During this project, SVW optimized its development process by extensively using CFD simulation to reduce aerodynamic drag in the very early phase of the project, i.e. the design of the upper body. Very often the interaction between styling and aerodynamics is an iterative procedure for finding a compromise between function and styling and a short response time for the aerodynamic evaluation is required.

In this paper we present the work which was done at Shanghai-VW for using computational aero-acoustic (CAA) simulation in the vehicle development process to assess and improve the buffeting behavior of a vehicle when the rear side window is open. In the first step, a methodology was established and validated against wind tunnel tests using a Sedan. The methodology consists of a calibration of the CAA model to represent the properties of the cabin interior of the real car in terms of damping, wall compliance and leakage followed by CAA simulations of the full vehicle at different wind speeds to obtain the transient flow field around the exterior shape and inside the passenger compartment. The interior noise spectra are directly calculated from the transient pressure inside the cabin.