This study investigates the effects of leading-edge shape on the excitation of the traveling crossflow mode in response to freestream slow acoustic waves in a Mach 6 flow over swept flat plates. Three leading-edge geometries are examined: one with a more blunt cylindrical nose, and two with less blunt ellipsoidal noses. Direct numerical simulations, combined with linear stability theory and parabolized stability equations, are used to investigate the receptivity process and downstream disturbance development for a target traveling mode. The steady base flow shows that increased nose bluntness leads to a larger favorable pressure gradient, which consequently results in greater amplification of the crossflow instability mode. The receptivity investigations reveal that the traveling mode is excited primarily within the rapidly varying mean flow region near the leading edge. Importantly, the abrupt surface curvature discontinuity induces a localized scattering effect on the evolution of the traveling mode, distorting its wavefront. This effect, however, becomes less pronounced with a milder surface curvature discontinuity among the three configurations. The receptivity coefficients for the cylindrical nose are noticeably smaller compared to those of the ellipsoidal cases. Nevertheless, the reduced initial amplitude of the traveling mode through receptivity is offset by enhanced downstream instability amplification. As a result, the more blunt cylindrical nose ultimately achieves larger disturbance amplitudes downstream.
Han et al. (Tue,) studied this question.