Turbulence Statistics in the Self-Preserving Region of an Axisymmetric Free Jet.

Abstract

Turbulence measurement was carried out in the self-preserving region of an axisymmetric free jet with the aid of the three-dimensional particle tracking velocimeter. Approximately 420 instantaneous velocity vectors on average were acquired from each of 126000 TV fields. The self-similarity and axisymmetry of turbulence statistics distributions are confirmed. The power-law requirements are fulfilled for the streamwise evolutions of the mean centerline velocity and the velocity half width. Detailed radial distributions of the turbulent statistics are obtained, which include mean velocities and all the one-point velocity correlations up to the fourth-order. Skewness and flatness factors of velocity fluctuations and the invariants of the Reynolds stress anisotropy tensor are also calculated. The mean radial velocity agrees with that calculated from the continuity equation and the mean streamwise velocity. The Reynolds shear stress is also in good agreement with that estimated from the momentum equation. These results demonstrate the accuracy and consistency of the present data.