Experimental Measurements and Quiet Direct Numerical Simulations on a Cone with an Inclined Slice and Compression Flap at Mach 6

This study details experimental and computational efforts aimed at furthering the understanding of separation bubble formation and reattachment behaviors on sliced cones with compression flaps. Typical cone-slice-flap bodies feature a slice cut parallel to the cone axis. In low-disturbance flow at Mach 6, this results in shear-layer separation that anchors to the slice leading edge, precluding investigation of an unanchored separation. In order to facilitate a favorable pressure gradient on the slice and an attached boundary layer, the slice was cut at an incline to the cone axis. Experiments were performed in the Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University, capturing data at a 0° angle of attack and a 15° compression flap angle. Freestream unit Reynolds numbers were captured in experiment at Re_∞ ≈ 2.7×10⁶ /m. A Quiet Direct Numerical Simulation was performed at Re_∞ ≈ 2.1×10⁶ /m. The discrepancy in compared Reynolds numbers is discussed, with the expectation that key laminar flow characteristics are preserved across the presented range of Reynolds numbers based on prior work with similar test articles. Heat transfer measurements revealed significant aerothermal loading and symmetric streaks of heating not apparent on conventional cone-slice-flap models, and were well predicted in computations. Finally, computational efforts predicted significant three-dimensional effects observed in experimental schlieren visualization that did not appear on the axis-aligned cone-slice-ramp variant. Future work will involve direct comparisons with additional Reynolds numbers, flap angles, and angles of attack, further enhancing the understanding of hypersonic shear-layer separation phenomena on highly three-dimensional test articles.