Numerical study of shock/boundary layer interaction in supersonic overexpanded nozzles

A numerical study, using a mixed finite element/finite volume method on unstructured meshes adapted for compressible flows, is conducted to investigate turbulent boundary-layer separation in overexpanded subscale supersonic nozzles including shock/shock and shock/boundary layer interactions. Two test-cases are investigated, namely a TIC (Truncated Ideal Contour) nozzle and a TOP (Thrust Optimized Parabolic contour) nozzle with a secondary jet injection. Particular attention is paid to the appearance of a recirculation region downstream of the Mach disc as well as in the vicinity of the secondary nozzle exit. The results so obtained are analyzed and compared with the experimental data. The results suggest that very different shock structures and flow separation may appear depending on the nozzle contour as well as on the operating pressure and temperature ratios. In the case of TOP nozzle, the simulations reveal the existence of a small recirculation bubble at the vicinity of the secondary injection, due to a shock/boundary layer interaction. In addition, it has been shown that, at high temperature ratios, compressibility effects on the growth rate of the mixing layer, which develops between the main stream and the secondary jet injection, become significant and cannot be neglected in the computation.