Flow model for predicting normal shock wave induced vortex breakdown

An analytical study of normal shock wave induced vortex breakdown has been undertaken. In this inviscid axisymmetric analysis, the response of supersonic streamwise vortices to imposed normal shocks has been determined by modeling the rotational core of the vortex as a slender, swirling layer. For vortex/shock combinations of increasing strength, the analysis predicts an ever increasing axial velocity deficit in the vortex core. Vortex breakdown is presumed to occur if a vortex/shock combination leads to flow stagnation at the vortex axis. The results of this study indicate that an inverse relationship exists between vortex swirl and freestream Mach number at breakdown. The breakdown limit curve generated using this analysis shows good correlation with established experimental results, indicating that the onset of normal shock wave induced vortex breakdown can be predicted with a relatively simple flow model and without recourse to numerical simulation. Interpretation of some normal shock wave/vortex interaction experiments in light of the predictions suggests that the phenomenon previously known as supersonic vortex distortion is a form of vortex breakdown.