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Reliable prediction of the radiated noise due to the air pressure pulsation inside air-intake manifolds (AIM) is of significant interest in the automotive industry. A practical methodology to model plastic AIMs and a prediction process to compute the radiated noise are presented in this paper. The measured pressure at the engine inlet valve of an AIM is applied as excitation on an acoustic boundary element model of the AIM in order to perform a frequency response analysis. The measured air pressure pulsation is obtained in the crank-angle domain. This pressure is read into MATLAB and transformed into the frequency domain using the fast Fourier transform. The normal modes of the structure are computed in ABAQUS and a coupled analysis in SYSNOISE is launched to couple the boundary element model and the finite element model of the structure. The computed surface vibration constitutes the excitation for an acoustic uncoupled boundary element analysis.

The goal of this study was to predict the unsteady forces acting on the plastic side-view mirror of a prototype vehicle traveling at a certain speed using computational fluid dynamics (CFD) techniques. These unsteady forces are flow induced because of the vortex shedding behind the mirror. It was observed during field testing that the mirror was vibrating excessively at certain speeds because of the unsteady forces. The frequency of vortex shedding depends on the geometry of the mirror and the angle of impingement of the incoming air. The initial step was to compute the steady state flow solution around the mirror. The pressure distribution on the mirror was used to compute the steady state flow forces on the mirror. In this CFD model most of geometric detail around the mirror were included which made the model very large. Unsteady solution could not be obtained because the model was very large for the available computational resources.