3-DIMENSIONAL BOUNDARY-LAYER-TRANSITION ON A SWEPT WING AT MACH-3.5

Transition on a swept-wing leading-edge model at Mach 3.5 is investiga ted. Surface pressure and temperature measurements are obtained in the NASA Langley Research Center Supersonic Low-Disturbance Tunnel. For o ne case, temperature-sensitive paint and a sublimating chemical are us ed to visualize surface flow features such as transition location, The experimental data are compared with 1) mean-flow results computed as solutions to the thin-layer Navier-Stokes equations and 2) N-factors o btained using the envelope e(N) method. The experimental and computati onal results compare favorably in most cases. In particular, N congrue nt to 13 correlates best with the observed transition location over a range of freestream unit Reynolds numbers and angles of attack. Comput ed traveling crossflow disturbances with frequencies of 40-60 kHz have the largest N factors, and the surface flow visualizations reveal smo oth transition fronts with only faint evidence of stationary crossflow vortices. These results suggest that transition is probably dominated by traveling, rather than stationary, crossflow disturbances for the present model.