The initial flow characteristics of supersonic jets with different geometries

• The three-dimensional initial flow fields of supersonic square and circular jets have been simulated numerically.
• The axis switching mechanism of square vortex loop has been illustrated and discussed.
• Both the axis switching and stream-wise vortices can enhance the entrainment and mixing of the square jet.

Based on large eddy simulation (LES) combined with the high-order hybrid schemes, the flow characteristics of both supersonic circular and square jets were investigated numerically for Ma=1.4Ma=1.4. Our results illustrate the three-dimensional (3D) structures and their evolutions of both circular and square jets, as well as the shock structures of both jets. Moreover, the phenomena of 45° axis switching and stream-wise vortices enhancing the entrainment and mixing process of the square jet were also identified and discussed in detail.