The starting flow structures and evolution of a supersonic planar jet

The starting flow fields produced by a supersonic underexpanded planar jet are studied numerically with the use of large eddy simulation (LES). The three-dimensional (3D) structures and evolutions of the starting jet flows including compressible main vortex pair, vortex-induced shock waves, shock-vortex interactions and jet mixing have been illustrated and discussed in detail. Our results show that the generation and evolution of the main vortex pair, the initial perturbation and the interaction of vortex-induced shock with jet shear layer can accelerate the instability and mixing of the shear layer. The geometric characteristics of the main vortex for different initial conditions have been discussed. Only at a later stage, the differences between the 2D and 3D structures of the vortex core are obvious, but the interface of the main vortex pair keeps stable even when the vortex cores become turbulent.