Development and validation of a phase shift and attenuation free filtering for exploitation of CFD data

A causal filtering method is developed to perform decimation and storage of aerodynamic data without signal distortion. When done without precaution, decimation of instantaneous computed flow fields for storage and subsequent exploitation generates aliasing. Use of a low-pass filter limits the creation of spurious noise but attenuates signal amplitudes and shifts phases. The proposed filtering method combines the application of a low-pass filter before decimation, during the aerodynamic simulation, with that of a corrective filter, applied in the frequency domain after the full storage. This corrective filter is designed to correct attenuation and phase distortion caused by the low-pass filter. The method is validated on analytical signals and successfully applied to turbulent shear layer and noise radiation problems.

► Signal decimation is required when storing computed flow fields for post-processing.
► Such decimation causes aliasing or signal distortion due to filtering.
► A causal filtering method with no attenuation or phase shift is developed.
► Causal filtering is first applied and signal distortions are corrected afterward.
► Validation is performed with a turbulent shear layer case and a noise radiation problem using an integral formulation.