A Review of the Design of Cone-Cylinder-Flare Geometries for Stability Analyses and Conventional/Quiet Wind Tunnel Tests

Abstract: In order to study the effects of pressure gradients, flow expansion, and recompression on the stability of hypersonic boundary-layers, axisymmetric cone-cylinder-flare configurations have been specifically designed for wind tunnel experiments. The objective is to create well-suited geometries for hypersonic laminar-turbulent transition analyses, while also adding the capability to generate attached and separated flows. After a thorough review of the aerodynamic flows obtained at Mach 6 and zero degree angle of attack in fully laminar conditions on each configuration, linear stability theory (LST) and linear parabolized stability equations (PSE) are used to predict the amplification rates of the boundary-layer disturbances for the case without flow separation since local stability analysis cannot handle highly non-parallel flows. For this attached flow case, the numerical stability results are compared to wind tunnel measurements obtained in the BAM6QT (Boeing AFOSR Mach-6 Quiet Tunnel). The semi-empirical method based on N-factor allows to correlate transition with the integrated growth of the linear instability waves. The influence of tunnel noise is also investigated, using conventional and quiet experiments.