Identify the slower convected disturbance responsible for narrow-band interference peaks

Identify the convected disturbance traveling at approximately 0.62 times the free-stream speed that generates the narrow, equally spaced interference peaks measured for perforated plates, and incorporate the corresponding convected source into the finite-chord leading-edge noise model.

Background

The finite-chord model reproduces the broadband noise-reduction level of the perforated plates but not the narrow, equally spaced spectral peaks observed in the measurements of Chaitanya et al. The peak spacing implies interference between the leading edge and a disturbance crossing the plate at a convection speed of approximately 0.62U, whereas the model contains only a frozen gust convecting at U.

The paper identifies two possible mechanisms—a secondary-vorticity disturbance generated at the leading edge and a hydrodynamic wave in the boundary layer over the perforation—but does not determine which mechanism is responsible. A corresponding convected source is absent from the present scattering formulation and would be needed to reproduce the measured narrow-band interference.

References

What the slower disturbance is has not been established.

— Leading-edge noise reduction by perforated and porous inserts: a compressible finite-chord prediction without fitted constants  (2609.36669 - Lee, 29 Sep 2026) in Section 4.3.2, “Diagnosis”; reiterated in Section 6, “Conclusions”