Multi-Instability Analysis of Swept-Wing Boundary Layers Part 2. Effects of Wall Curvature and Nonparallelism on the e^N Method

Abstract

Multi-instability characteristics of the three-dimensional boundary layer around a yawed circular cylinder are investigated by an e^N method involving the effects of wall curvature and nonparallelism. Velocity profiles of the boundary layer are approximated by members of Falkner-Skan-Cooke similarity solutions and the local dispersion relation of each member is determined from the nonparallel eigenvalue problem proposed in part 1 of this study. A complex ray theory is adopted in the integration procedure for N factor, and a numerical estimation of N is made to describe wedge-shaped disturbances originating from a point source. The analysis using these methods shows that the influence of wall curvature and nonparallelism stabilizes and destabilizes the flow, respectively, though their quantitative effects on the N factor depend on kinds of instability, range of frequency, and values of flow parameters. It is also found that the destabilizing effect of nonparallelism increases with the increase of sweep angle.