  This study performs global stability/receptivity analyses of hypersonic sweep
flows around a blunt body with an infinite span. For the first time, we obtain
the characteristics of the leading attachment-line mode to the variation of
sweep angles from 20 to 70 degrees. The global eigenfunctions exhibit the
characteristics of the attachment-line instability at the leading edge. At the
same time, cross-flow (at small sweep angles) or second Mack mode (at larger
sweep angles) dominates further downstream. We establish an adjoint-based
bi-orthogonal eigenfunction system to address the receptivity problem of such
flows to any external forces and boundary perturbations. The receptivity
analyses indicate that the global modes are the most responsive to external
forces and surface perturbations applied in the vicinity of the attachment
line, regardless of the sweep angles. It is also proved that the present global
extension of the bi-orthogonal eigenfunction system can be successfully applied
to complex flows.
