Abstract: The flow fields of 2-D compressible axisymmetric jet are simulated by solving N-S equations. The discretization method has high order accuracy. The information and development of the large vortical structure and it's role in the jet development are studied. The Kelvin-Helmholtz wave appears firstly when jet losts it's stability, and then the single vortex rolls up. After that, with the development of jet, the vortex structures begin to pair and merge because of the increasement of non-linear effects. It is also shown that the pressure distribution is directly relative to the large vortical structures.

Key words: jet, large vortex structure, upwind compact scheme, symmetrical compact scheme, vortex pairing, vortex merging