Turbulent mixing and trajectories of jets in a supersonic cross-flow with different injectants

We investigate flow fields and trajectories of sonic jets in a supersonic cross-flow with different injectant properties. The cross-flow is held at a fixed condition with Mach number 1.71, static temperature similar to 375 K and static pressure similar to 76 kPa. Jet conditions cover momentum flux ratios J from 1 to 6, molecular weights from similar to 4 to 44gmol(-1) and specific heat ratios from similar to 1.24 to 1.66. Mie-scattering images are used to study turbulent mixing and trajectory development. Qualitative trends suggest that, at J = 4-6, the convective Mach number concept applies as discussed in previous literature. At lower J, however, trends for changing molecular weights seem to reverse and the boundary layer might influence turbulent mixing. Analytically estimated jet velocities suggest the suppression of hydrodynamic instabilities changes at different rates for different injectants, as J increases. A newly developed, semi-empirical jet trajectory scaling explicitly considers the momentum flux ratio, boundary layer effects and the existence of the jet bow shock. For validation, this scaling is applied to our trajectory data and those of existing literature, extending the covered parameter space. Quantifying the degree of trajectory correlation shows the scaling is specifically relevant at J <= 6 in this study, where the boundary layer and bow shock influence are important. On the other hand, at higher J and for thin boundary layers, the momentum flux ratio plays a more dominant role. The results in this study can guide the design of injection systems for supersonic applications and improve prediction of jet trajectories.

Automated summary

The study investigates flow fields and trajectories of sonic jets in a supersonic cross-flow with different injectant properties. Results show that different factors have varying influences at different J values, with boundary layer and bow shock playing key roles in trajectory development.