Low and High Level Acoustic Propagation in Waveguides: Vibroacoustic Coupling in a Bent Pipe at Low Frequency

In industrial energy production sites, the manufacturing processes induce the use of piping networks subject to strong environmental constraints (transport of dangerous gases at high pressure and high temperature). Reciprocating compressors connected to these networks behave like acoustic sources whose pulsations induce vibrations of structures by coupling between the gas column and the piping system. This vibro-acoustic coupling occurs especially when two bends are separated by a straight pipe. Usually, The industrial objective is to estimate the vibration field of an piping system submit to a sound pressure field in order to pre-dimension the global structure. However, although little described in the literature, an acoustic model based on the plane wave hypothesis is generally accepted in order to estimate the resultant forces applied on an elbow. These works therefore focuses on the experimental study of the vibro-acoustic coupling phenomenon when piping is subjected to a low or high sound pressure field. The aim is thereby to highlight the impact of a non-linear acoustic propagation on the vibration field on a piping system. Then an FDTD (Finite Difference Time Domain) model of non-linear pressure field resolution associated with a mechanical modal synthesis model is described to correctly estimate this vibration field.