Effects of Grooved Walls on High-Speed Boundary Layer Transition on a Slender Cone — Simulations and Experiments

In this paper, we examine the stabilizing effects of large-scale 2D porous walls termed "grooves" on disturbances in a Mach 6 hypersonic boundary layer over a 3 degree half-angle cone. The grooves are defined analytically using sinusoidal and cosinusoidal functions (referred to as s-type and c-type). Stability characteristics are investigated using linear stability theory and time-spectral disturbance calculations. To gain further insight into the mechanisms behind the (de)stabilizing effects of the grooved walls an energy budget analysis is carried out, where specific production and dissipation mechanisms are evaluated for the two groove designs. Initial results show a strong reduction in the wall pressure amplitude for the s-type groove design, whereas c-type grooves worked to briefly stabilize the flow downstream before sharply destabilizing beyond the smooth wall case. These results are compared against experimental data collected in the Boeing-AFOSR Mach 6 Quiet Tunnel (BAM6QT) at Purdue University to provide comparison against computational results. The experiments show a reduction through the presence of the grooves but not as much as observed in the simulations.