The sound properties of modern cars play an increasingly important role on the overall impression of a vehicle. One of the major sound sources is hereby the exhaust system, which is exposed to large pressure pulsations resulting from the periodically blown out exhaust gas of the car engine. These large pressure pulsations lead to vibrations of the thin walls of the exhaust system and thus create another sound source which is additionally contributing to the sound radiation of the exhaust system. In this work, the sound radiation of an idealized exhaust system is analyzed. The sound transmission within the exhaust system is simulated by using fully coupled FE-FE-models. For the succeeding solution of the exterior acoustic problem the Fast-Multipole BEM (Boundary Element Method) is employed. This work focuses on the contribution of the vibrating structure to the overall sound radiation. It is found that close to some resonance frequencies of the in-vacuo structure there is a significant contribution of the vibrating structure to the overall radiated sound power. For the employed weakly coupled computation of the acoustic interior and exterior problem a radiation impedance condition needs to be applied on the outlet of the exhaust system. In this work a FEM-BEM relaxation scheme is proposed to obtain an element wise radiation impedance condition for arbitrary cross-sections.
Acoustic-structure simulation of exhaust systems by FEM and Fast-BEM
Schall-Struktur-Simulation von Abgassystemen mittels FEM und schnellem BEM
2005
7 Seiten, 7 Bilder, 7 Quellen
Conference paper
Storage medium
English
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