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Wednesday, July 10 • 18:10 - 18:30
EXPLICIT FILTER DESIGN FOR AEROACOUSTICS SIMULATIONS ON UNSTRUCTRUED GRIDS USING THE Z-TRANSFORM

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Explicit spatial filters can be used to stabilize aeroacoustics simulations, specially for Large-Eddy Simulations (LES), to remove energy from high wavenumbers. Filter design for unstructured grids has proven to be elusive as there is no systematic method to know the filter performance a priori. A filter design procedure based on multi-dimensional Z-transform with non-uniform sampling in the wavenumber domain was developed and presented for the first time. A canonical elliptic differential equation was used as the kernel for spatial filtering. It was discretized using the Finite Element Method (FEM). A multi-directional projection was used to reduce the problem into several one-dimensional Z-transforms, determining some of the filter parameters to ensure full attenuation at the grid cut-off in all numerical directions. Remaining parameters were selected to control the filter cut-off wavenumber. The impact of local grid anisotropy on the design procedure and the dissipation and dispersion properties of the filter was investigated. It was found that ideal filter properties for an asymmetric grid topology require complex filter parameters. Modified dissipation and dispersion properties when using only the real part of filter parameters, rather than the full complex number, was investigated for several typical two- and three-dimensional asymmetric grid topologies. Preliminary numerical results were obtained for the Comte-Bellot and Corrsin's decaying homogeneous isotropic turbulence using designed filters on a perturbed structured grid as well as on a fully unstructured grid.

Moderators
GG

Gwenael Gabard

Dr., LAUM, Le Mans Université

Authors

Wednesday July 10, 2019 18:10 - 18:30 EDT
Outremont 5
  T03 Aero… aircrft noise & vibr., SS02 Computational Aeroac