Numerical Boundary-Layer Stability Unstable First Mode Detection for the Reentry-F Cone

Investigations on the boundary-layer stability of the Mach 19.925 Reentry-F cone are performed in this article. To enable these calculations, first, the base flow solver and the boundary-layer stability solver are validated for the perfect gas and the thermochemical equilibrium gas regime. Thereafter, computations of the linear stability theory along the Reentry-F cone are performed, and the results are compared against results found in the literature. Comparable to these referenced results, second and third Mack modes are found along the geometry, but in contrast, an additional peak of the growth rate arises upstream of the second mode in the current calculations. Thus, further investigations are performed on the nature of this additional peak. The results show that, with respect to the phase speed and the disturbance pressure eigenfunctions, the additional peak corresponds to the first mode, which in the current case has unstable behavior and in consequence has a major influence on the boundary-layer stability development along the Reentry-F cone, respectively, for high-hypersonic Mach number flows.