Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2026 number 1

The distributed receptivity of a swept-wing laminar boundary layer to unsteady freestream vortices with a longitudinally oriented vorticity vector in the presence of uniform spanwise surface undulations is experimentally investigated. Experiments are performed on a 25° swept-wing model under fully controlled disturbance conditions. Unsteady longitudinal freestream vortices are found to induce highly efficient distributed (in the streamwise direction) excitation of unsteady cross-flow instability modes at combination spanwise wavenumbers. This excitation results from vortex scattering by surface inhomogeneities. Part 1 of this study (published in the previous issue of the journal) describes the experimental approach and its theoretical justification; the experimental setup; the mean flow structure; the method of disturbance generation; the characteristics of freestream and surface disturbances; experimental evidence for the high efficiency of the investigated receptivity mechanism; the important role of longitudinal wavenumber resonance in exciting the most amplified cross-flow instability modes. Part 2 of this study (the present paper) presents the experimental determination of the amplitudes and phases of the distributed vortex-roughness receptivity coefficients as functions of disturbance frequency and spanwise wavenumber. Receptivity coefficients responsible for cross-flow wave excitation on a smooth surface are also obtained, and the relative efficiencies of the distributed vortex receptivity and vortex-roughness receptivity mechanisms are compared. The results are further compared with those previously reported for distributed vortex receptivity on a smooth surface.