Modelization of immersed structures at arbitrary positions in an acoustic fluid using XFEM
Noise reduction for passengers comfort in transport industry is now an important constraint to be taken into account during the design process. This process involves to study several configurations of the structures inside a given acoustic cavity in the context of an optimization, uncertainty or reliability study for instance. The finite element method can be used to model this coupled fluidstructure problem but needs an interface conforming mesh for each studied configuration which may become time comsuming. The aim of this work is to be able to efficiently analyze different configurations of structures immersed in the acoustic domain and their influence on the noise level in the cavity. The embeded structures, such as seats in a plane cabin, are assumed to have no thickness in the acoustic domain: they are seen by the fluid as surfaces. The XFEM is used to take into account the structure influences in the acoustic compressible fluid domain by enriching the pressure by a Heaviside function. This makes the parametric study easier since it does not involved a meshing process anymore.
Two thin shell structures immersed in an acoustic fluid

Fluid mesh incompatible with mesh structures

Fluid enriched elements with the Heaviside function

Pressure field to a given harmonic excitation on one structure

Frequency response function of the acoustic cavity

Reference:
A. Legay, An extended finite element method approach for structuralacoustic problems involving immersed structures at arbitrary positions, International Journal for Numerical Methods in Engineering, in press, 2012. doi