Measurements on Cone-Flare Geometries in the Supersonic Low Disturbance Tunnel

Four different cone-flare-cylinder models were tested in the NASA Langley Research Center Mach 3.5 Supersonic Low Disturbance Tunnel. The goal of this campaign was to assess differences in SBLI-induced flow separation and reattachment for a 7-deg half-angle cone, with flare half angles of 16, 20, 24, and 28 degrees. The cone portion of the models was 19.2% scale of the ROTEX-T flight geometry, while the flare portion was extended from that scale to promote flow reattachment. The 20-deg flare model was machined of polyether ether ketone (PEEK) with a stainless steel nosetip. The other three models were printed of clear resin. The models were tested in both quiet and conventional conditions with nominally zero pitch and yaw. The model surface temperature time history was measured using infrared thermography and thermocouples at various unit Reynolds numbers ranging from 2.1-24.0 M/m. The locations of separation on the cone and reattachment on the flare were observed for most conditions in quiet flow; however, the heating signature from the reattachment shock was absent for 16-deg and 20-deg lower Reynolds number cases. As the unit Reynolds number increased, both separation and reattachment converged to the cone-flare interface, with separation farther upstream and reattachment closer to the junction with increasing flare angle. In conventional flow, a similar trend occurred, albeit at lower unit Reynolds numbers, and by Re = 13.5 M/m, boundary-layer transition advanced to the cone portion of all four models. High-speed schlieren images acquired at 150 kHz were also used to assess separation and reattachment locations. The filtered back projection technique was used to evaluate density gradients above the center plane of the model. Axisymmetric flow solutions were computed for unit Reynolds numbers between 4.7-11.9 M/m. In general, the separation and reattachment locations determined from computations compared favorably with those estimated from the heat-flux maps and the schlieren images acquired in quiet flow at lower Reynolds numbers, as long as the interaction was laminar.