EXPERIMENTAL INVESTIGATION OF BOUNDARY LAYER TRANSITION ON CONE-FLARE GEOMETRIES AT MACH 4

Abstract

This study investigates supersonic boundary layer transition on a cone-flarewith a 5° half-angle straight cone and flared bases of +5°, +10°, and +15°. The experiments used the University of Maryland's Multiphase Flow Investigations Tunnel (MIST), a Mach 4 Ludweig tube. Experiments were performed “dry”, without aerosols or droplets, and focus on the first-mode (Tollmien-Schlichting) boundary layer instability waves and their interaction with the compression corner. Using high-speed Schlieren imaging, the boundary layer dynamics on the cone-flare's top surface were analyzed. The data were processed through Power Spectral Density (PSD) and Spectral Proper Orthogonal Decomposition (SPOD) techniques to study the behavior of the first-mode waves and the transition location changes. The findings reveal coherent wave packets within the boundary layer at frequencies characteristic of the first-mode. The wave packets power increased along the cone and peaked near the compression corner before dissipation on the flare. These findings contribute to the understanding of first-mode boundary layer transition mechanisms in hypersonic flows for the cone-flare geometry.