Flow–Porous Interaction of a Blunt Trailing-Edge Subject to an Asymmetric Grazing Flow

Kurzfassung

Porous trailing-edge treatments are commonly investigated under symmetric grazing-flow conditions, where comparable boundary layers develop on both sides of the edge. In many practical applications, however, the incoming flow is asymmetric, with a developed boundary layer present on only one surface. The present study examines the flow-porous interaction of a blunt structured porous trailing edge subjected to such an asymmetric grazing flow. Experiments were conducted in an aeroacoustic open-jet wind tunnel using far-field microphone measurements and hot-wire anemometry, with selected comparisons made against previously published data for a similar porous configuration under a symmetric grazing flow. The acoustic results reveal a dominant pore-scale tonal component at higher pore-scale Reynolds numbers, centered at $St_{p} \approx 0.15$, together with a sequence of weaker broadband humps at higher Strouhal numbers, suggesting a harmonic-like aeroacoustic response associated with grazing-flow interaction with the porous structure on the upper surface. Directivity over both the primary tonal band and higher-frequency band is dipole-like, consistent with trailing-edge scattering. The near-wall flow field shows that, relative to the symmetric case, the asymmetric inflow drives the shear layer more rapidly toward the wake centerline and produces localized streamwise flow penetration only within the uppermost pore depth immediately downstream of the trailing edge. Spectra of streamwise velocity fluctuations further indicate local shedding processes near the trailing-edge corner with a characteristic length scale linked to the pore-strut thickness. These preliminary findings provide new physical insight into how asymmetric grazing flow modifies the near-wall flow topology and radiated noise of blunt-structured porous trailing edges.