Budgets of the Reynolds Stresses in an Axisymmetric Free Jet.

Abstract

In the previous study an axisymmetric free jet was measured with the aid of a three-dimensional particle tracking velocimeter, and a database of the turbulent statistics was constructed. In this study, by using the database, the budgets of the turbulent kinetic energy and the Reynolds normal and shear stresses are calculated. The dissipation term of the turbulent kinetic energy is estimated as a residual of its budget neglecting the pressure diffusion term. The pressure terms in the budgets of the Reynolds stresses are also obtained as closing terms of each budget equation in which the dissipation term is calculated with an assumption of local isotropy. The mechanism of energy exchange among the stresses is revealed, i.e., the mean flow energy is first fed to the streamwise normal stress through the Reynolds shear stress and then redistributed to the radial and azimuthal normal stresses via the pressure term. The production terms in the budgets of the radial and azimuthal stresses are found to be negative around the flow axis.