Application of the POD to the similarity region of an axisymmetric turbulent jet

Multipoint instantaneous measurements of the streamwise velocity component were obtained in the far field region of an axisymmetric turbulent jet from 20 to 69 diameters downstream for jet exit Reynolds numbers ranging from 40,000 to 84,700. The Proper Orthogonal Decomposition (POD) was then 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 62% of the resolved streamwise energy, has two peaks: one at azimuthal mode-2 at near zero frequency, and another at mode-1 at a local Strouhal number (fx/U_c) of approximately 1. When checked against two-point statistics similarity analysis from Ewing (1995) extended to the POD, the results compare favorably and also give some hints into the resolution necessary to cover the field.