ACOUSTIC POSTPROCESSING FOR MULTIBODY SIMULATIONS INCLUDING FLEXIBLE BODIES

Abstract

In this paper an acoustic postprocessor for multibody simulations is presented. The tool computes the sound power on the surface of a generic vibrating flexible body. The radiated sound power is not computed because this would require the knowledge of the radiation efficiency. Such parameter can be determined by an ulterior analysis including the fluid/structure interface, to be performed by an appropriate Finite Element or Boundary Element analysis. The sound power computed by the presented tool can be directly used for the relative acoustic assessment of mechanical parts with respect to design variations or modified boundary conditions. Moreover, the computed sound power directly leads to an estimate of the radiated power – and thus eventually of the noise level – if the radiation efficiency can be deduced from experience or empiric formulas, which is the case of most engineering problems. As an application example, the acoustic behavior of a railway wheelset is studied. The wheelset is modeled as a flexible body and integrated in the multibody model of a complete vehicle. Two operative cases have been considered: first, the vehicle driving through a switch, with the resulting impulsive noise due to the wheel rolling over the rail gap in the middle of the switch (“frog”); secondly, the rolling noise due to wheel and rail roughness – a dramatic problem especially for freight vehicles.