Title: Prediction of Aeroacoustical Interior Noise of a Car, Part-2 Structural and Acoustical Analyses
text: One-way coupled simulation method that combines CFD, structural and acoustical analyses has been developed aiming at predicting the aeroacoustical interior noise for a wide range of frequency between 100 Hz and 4 kHz. Statistical Energy Analysis (SEA) has been widely used for evaluating transmission of sound through a car body and resulting interior sound field. Instead of SEA, we directly computed vibration and sound in order to investigate and understand propagation paths of vibration in a car body and sound fields. As the first step of this approach, we predicted the pressure fluctuations on the external surfaces of a car by computing the unsteady flow around the car. Secondly, the predicted pressure fluctuations were fed to the subsequent structural vibration analysis to predict vibration accelerations on the internal surfaces of the car. Finally, an acoustical analysis was performed to predict sound fields in the cabin by using particle velocities of sound on the interior surfaces of the car, predicted by the structural analysis. To transfer predicted surface data, such as pressure fluctuations, vibration accelerations and particle velocities of sound, from one simulation to another, we adopted a parallel coupling tool. As the second part of our research, this paper presents results of the structural vibration analysis and that of the acoustical analysis, together with those measured by wind tunnel tests. In our research, a light automobile, for which all the interior components were removed and the underfloor shape was simplified, was employed for a case study. The wind tunnel tests were performed with a freestream velocity of 100 km/h. Both the predicted interior surface accelerations and interior noise level agreed well with the measured equivalents up to 2 kHz.