Boundary-Layer Instabilities on a Supersonic Finite-Span Swept Wing

This paper investigates the stability of the boundary layer over a finite-span 65 deg swept wing at Mach 2 and a unit Reynolds number [Formula: see text] with one- and two-dimensional stability analyses. Three branches of instabilities are identified: Tollmien–Schlichting (T–S) modes, crossflow ([Formula: see text]) modes, and connected modes. The connected modes are embedded within the Tollmien–Schlichting and crossflow branches. The T–S modes lie in the vicinity of the leading edge or attachment line ([Formula: see text]) with frequencies larger than [Formula: see text]. The [Formula: see text] modes peak at a significantly large distance away from the leading edge with the most unstable frequency around [Formula: see text] and much smaller growth rates than the T–S modes. The [Formula: see text] connected modes have two amplitude peaks in the attachment line as well as at a position slightly away from the attachment line and exhibit very high frequencies beyond [Formula: see text]. The [Formula: see text] or [Formula: see text] connected modes have an additional amplitude peak in the vicinity of the attachment line. The growth rates of [Formula: see text] connected modes are comparable with the T–S modes, whereas the [Formula: see text] or [Formula: see text] modes are significantly less unstable than the [Formula: see text] modes. This study enriches the physical mechanisms and instabilities involved in supersonic swept wings.