Receptivity and stability of hypersonic leading-edge sweep flows around a blunt body

TL;DR

This paper investigates the stability and receptivity of hypersonic sweep flows around a blunt body, revealing how different instability modes dominate at various sweep angles and identifying regions most responsive to external disturbances.

Contribution

It introduces a global stability and receptivity analysis for hypersonic sweep flows, including the first characterization of attachment-line modes across a range of sweep angles.

Findings

Attachment-line instability characteristics vary with sweep angle.

Global modes are most sensitive near the attachment line.

The bi-orthogonal eigenfunction system effectively analyzes complex flows.

Abstract

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.