Recent interpretation of coherent structures in initial region of free turbulent jet is summarized.
Measurements of mean velocity, axial fluctuation velocity are reported in the developing region of coaxial jet flows issuing from concentric long round pipes into still air.
The measurements were obtained with 4 velocity ratios, i.e., values of the maximum initial pipe velocity to maximum annulus velocity of 0, 0.62, 1.24, 2.2
After a downstream distance about x/Do - 10, The turbulent jet mixing process begins to forget their initial condition, i.e. the turbulent structure becomes almost identical regardless of the initial velocity ratio