Instantaneous measurements of the streamwise velocity component were obtained in the far field region of an axisymmetric turbulent jet at exit Reynolds numbers ranging from 40 000 to 84 700. The data were taken from 20 to 69 diameters downstream of the jet exit using 138 hot-wires. The proper orthogonal decomposition was applied to a double Fourier transform in time and azimuthal direction of the two-point velocity correlation tensor. The first eigenspectrum, which contains more than 60% of the

more »

... kinetic energy, has two peaks: A dominant peak at azimuthal mode-2 at near zero frequency, and a secondary peak at mode-1 at a local Strouhal number ( f x/U c ) of approximately 1. The most striking feature was the general behavior of the eigenspectra: when normalized to reflect the energy repartition per mode number only, they peaked at mode-2, and were independent of downstream position in the experiment considered. They were also similar in nature to those obtained in earlier experiments at x/Dϭ6, just past the end of the potential core, but distinctly different from those closer to the jet exit where mode-0 and higher modes dominated.