Abstract
Based on the results from direct numerical simulation (DNS), the effects of initial conditions (i.e. the Reynolds numbers and the mean velocity profile at the jet exit) on coherent structure (CS) and flow evolution of turbulent plane jets are analysed. The strength, scale and pattern of CS are observed using the vorticity data and the vortex eduction schemes based on the low-pressure isosurfaces and Q-criterion. The effects of large scale CS on the decay of mean velocity, turbulent fluctuation and the mean momentum transportation are also clarified in this study. The results suggest that CS in the turbulent plane jets are mainly of two types: spanwise and streamwise vortices, whose patterns are line and helix, and in the transition process CS will act the main role, which is on the higher energy level compared with the non-coherent structure, and beneficial for the mean momentum transport. The decrease of Re and the setting of parabola velocity profile at jet exit will enhance the strength of CS.
