Initial region of a turbulent coaxial jet was experimentally investigated by using a constant-temperature hot-wire anemometer system with a linearizer.
Three different types of axisymmetric jets have been studied ; namely, single jet, annular jet and coaxial jets with different mean velocity ratios.
Mean velocity, turbulent intensities in both axial and radial directions and Reynolds stress have been measured to study the turbulent structures of these jets.
It was found that the coaxial jet developes more rapidly than a single jet and that the distributions of mean velocity, turbulent intensities and Reynolds stress are closely related to each other.
Particularly, the length of inner potential core was found to be dependent on the velocity ratio between the two streams.
After a downstream distance about x/Do of 6~8, the mixing process of the jet begins to forget its initial condition and the distributions of mean velocity, turbulent intensities and Reynolds stress tend to be self-similar far downstream.
