A Study of Three-Dimensional Shear-Layer Separations in Mach-6 Quiet Flow

Experimental andcomputationaleffortsaimedatadvancingtheunderstandingofseparation behavior on sliced cones with compression ramps were conducted in this work. To create a favor able pressure gradient along the slice and delay separation, a slice inclined at a 4° angle relative to the cone axis was introduced. Experiments were conducted in the Boeing/AFOSR Mach-6 Quiet Tunnel at i) angles of attack of up to 2°, ii) compression ramp angles of 10°, 15°, and 20°, and iii) freestream unit Reynolds numbers ranging from Re∞≈2.7×10⁶/m to Re∞≈11.5×10⁶/m. Schlieren videography was captured at 100 kHz to provide off-surface visualization of the separation bubble. Infrared thermography measurements revealed significant aerothermal loading and highly Reynolds-number-dependent streak formation; however, the separation length was shown to demonstrate minimal change to the variance in Reynolds number. Quiet Direct Numerical Simulations conducted in US3D at unit Re∞=2.7×10⁶/m provided insight into the structure of the three-dimensional separation bubble and the underlying mechanisms driving these phenomena in the laminar regime.