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 de termined by modeling the rotational core of the vortex as a slender, s wirling layer. For vortex/shock combinations of increasing strength, t he analysis predicts an ever increasing axial velocity deficit in the vortex core. Vortex breakdown is presumed to occur if a vortex/shock c ombination Leads to how 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 cu rve generated using this analysis shows good correlation with establis hed experimental results, indicating that the onset of normal shock wa ve induced vortex breakdown can be predicted with a relatively simple flow model and without recourse to numerical simulation. Interpretatio n of same normal shock wave/vortex interaction experiments in light of the predictions suggests that the phenomenon previously known as supe rsonic vortex distortion is a form of vortex breakdown.