The Effects of Controlled Harmonic Morphing on a Porous Trailing Edge

The aeroacoustics of a morphing trailing edge are investigated numerically using a two-dimensional Unsteady Reynolds Averaged Navier-Stokes (URANS) model, to assess the effects of combined harmonic morphing and porosity on the sound generated. Experiments performed in an open-jet facility, using open-cell metal-foam trailing edges are used to validate the numerical modeling of the porous regions. While the acoustic set-up is validated with experimental results of a NACA 0012 finite wing in an anechoic wind tunnel, as well as additional computational models of the same test case. The porous model is then implemented in the baseline acoustic model, and the same harmonic motion is applied to the baseline solid trailing edge test case, a 120PPI trailing edge case, and a 80PPI trailing edge case. The morphing of the trailing edge is numerically performed through the use of dynamic meshing in the commercial software StarCCM+. Results show a reduction in noise at frequencies under 1kHz between the morphing solid and the porous cases, while an increase in sound pressure levels can be seen on the porous cases due to the morphing with respect to the solid case. This indicates that the porous surfaces break down the larger turbulent scales created by the morphing, attenuating the increase in low-frequency noise that is present in the solid test case, and increasing noise at higher frequencies due to the presence of smaller turbulent scales.