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A numerical method to simulate aeroacoustic fields around automobiles is proposed in the present paper. The proposed method can be used to compute sound emissions directly in both far fields and near fields. Sound passes through body structures near A-pillars and rear-view mirrors. The direct predictions of the sound to passengers therefore require solutions of acoustic near fields. Most aeroacoustics simulations around automobiles are based on Lighthill's analogy. Strictly speaking, Lighthill's analogy is not consistent in near fields because near fields are not governed by a simple wave equation. In the present paper, a proper approach is proposed to achieve further progress in the simulation of aeroacoustic fields around automobiles. The difficulties occur because the sound pressure is much smaller than the vortical flow pressure.

Dynamic wind-tunnel tests of a simplified passenger car model were conducted using a two-degree-of-freedom model shaker. Time-resolved aerodynamic loads were derived from a built-in six-component balance and other sensors while the model underwent sinusoidal heaving and pitching motions at frequencies up to 8 Hz. The experimental results showed that frequency-dependent gains and phase differences between the model height/angle and the aerodynamic loads are in close agreement with those predicted by large-eddy simulation (LES) using an arbitrary Lagrangian-Eulerian (ALE) method. Based on these findings, transient aerodynamic loads associated with lateral motions were also estimated by LES analysis. Based on the above results, a full-unsteady aerodynamic load model was then derived in the form of a linear transfer function. The force and moment fluctuations associated with the vertical and lateral motions are well described by the full-unsteady aerodynamic load model.