Transverse gas jet injection behind a rearward-facing step

An experimental and theoretical study of the behavior of a transverse gas jet injected behind a rearward-facing step in supersonic flow is described. In-flight iodine planar laser-induced fluorescence imaging was performed to study this flowfield at NASA Dryden Flight Research Center using a flight test fixture situated under the fuselage of an F-104G aircraft. Jet structure and penetration data were obtained, in addition to limited characteristics for jet mixing and for supersonic flow over a rearward-facing step in a flow regime and for injection locations not extensively studied in the past. A model for jet behavior is described that places emphasis on the dynamics of the vortical structures observed to dominate jet cross section. The complex flowfield formed downstream of the step is represented by a combination of empirical and analytical correlations. Model predictions for jet trajectories compare reasonably well with results from the present in-flight experiments as well as with prior wind-tunnel experimental data.