Analysis of the noise source interpolation within a hybrid CAA method: application to the case of the Helmholtz resonator

This contribution reports on investigations to validate a computational aeroacoustics methodology. An acoustic analogy is adopted in which the Cenaero flow solver Argo is coupled to the commercial acoustic solver Actran/LA that uses a variational formulation of the Lighthill analogy. Two approaches to transfer noise sources from the fluid dynamics mesh to the acoustic mesh are studied. The first approach is based on a linear interpolation of the acoustic sources. Although this method ensures a second order accuracy, the conservation of the source term integral from one mesh to another is not fulfilled. Previous work shows that this leads to requirements on the acoustic mesh resolution in the source region that are more severe than those to properly propagate the acoustic waves. The second approach, newly developed by Free Field Technologies, is designed to enforce the conservation of the integral of the source term so that no particular mesh refinement is required in the source region, leaving the propagation as the only criterion to design the acoustic mesh. Both approaches are compared for the computation of the noise radiated by a Helmholtz resonator placed in a duct.