Transformation of spectra of refraction index fluctuations in axisymmetric supersonic jet with the increase in the distance from the nozzle

Abstract

In this paper the results of reconstruction of the radial dependence of refraction index fluctuations spectra in axisymmetric supersonic jet from laser transillumination data are presented. The reconstruction algorithm uses experimental spectra of laser radiation, received behind the jet, and the distribution of time-averaged axial air velocity within the jet. Laser transillumination experiments were performed on the Vertical Jet Unit of ITAM SB RAS (Novosibirsk, Russia). Reconstruction results show the refraction index spectra obey the power-law model, with power index different from that of the Kolmogorov turbulence model (−11/3). Within the first two barrels of the jet the power index is changing from ~−1 near the nozzle to ~−2.7 near the second Mach disk. Also some variations of power index and amplitude coefficient with the distance from the jet axis are found.