Improved understanding and control of high-speed jet interaction flows



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Texas A&M University


A numerical study of the flow field generated by injection through diamondshaped orifices into a high-speed flow is presented in this document. Jet interaction flows have a wide range of applications in the field of engineering. These applications include the use of jets for fuel injection in scramjets, for reaction control of high-speed aerodynamic bodies and as cooling jets for skins of high-speed vehicles. A necessary requirement in the use of transverse jets for these and other applications is a thorough understanding of the physics of the interaction between the jet and freestream. This interaction generates numerous flow structures that include multiple shocks, vortices, recirculation regions and shear layers. This study involves diamond-shaped orifices that have the advantage of generating weaker or attached interaction shocks as compared to circular injectors. These injectors also negate the effects due to the recirculation region that is formed upstream of the injector. This study was undertaken in order to gain further understanding of the flow features generated by diamond-shaped injectors in a high-speed flow. Numerical simulations were performed using two different levels of turbulence models. Reynolds? Averaged Navier-Stokes (RANS) simulations were performed using the GASP flow solver while Detached-Eddy Simulation (DES) runs were performed using the Cobalt flow solver. A total of fifteen diamond injector simulations were performed using the RANS model for a 15 half-angle diamond injector. The fifteen simulations spanned over five different injection angles and three jet total pressures. In addition to these, two circular injector simulations were also performed. In addition, low pressure normal injection through diamond and circular orifices simulations were performed using DES. Results obtained from CFD were compared to available experimental data. The resulting flow structure and the turbulent properties of the flow were examined in detail. The normal injection case through the diamond-shaped orifice at the lowest jet total pressure was defined as the baseline case and is presented in detail. In order to study the effect of different components of the vorticity transport equation, an in-house code was used post-process the results from the RANS runs.