Turbulence Production and Energy Transfer Mechanism in the Transition Process of a Two-Dimensional Jet

Abstract

The effects of coherent vortices on turbulent energy transfer were examined in an acoustically excited two-dimensional parabolic jet. Production terms in the energy transport equation were evaluated based on the results of hotwire conditional measurements. Difference in vortex arrangement gave significant influence on the energy transport process among mean flow, coherent structure and incoherent turbulence. When the symmetrical vortex arrangement was excited, most of the mean flow energy directly dissipated into random incoherent turbulence. For the anti-symmetrical mode, large amounts of positive and negative turbulent energy fluxes were produced around strong large-scale coherent vortices. Fine-scale vortices between the streamwisely adjacent coherent vortices played important roles in the turbulent energy transport process for the anti-symmetrical vortex arrangement.