The structure of dissipative scales in axisymmetric turbulent gas-phase jets

Results are reported for an experimental study directed at investigating the fine scale structure of turbulent jet flows using the simultaneous imaging of the concentration and velocity fields. The measurements are obtained in an axisymmetric coflowing jet using particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) imaging of acetone vapor seeded into the jet gas. The measurements resolve the Kolmogorov scale, η, of the flow. These measurements are used to investigate the relationships among the vorticity, strain rate, kinetic energy dissipation, and scalar dissipation fields. The data are also used to analyze the physical size of the structures in the scalar and kinetic energy dissipation fields. The results show good correlation between regions of high compressive principal strain, scalar dissipation, and kinetic energy dissipation. Structures in the scalar dissipation field are seen to be sheet-like with thicknesses ranging between 1η and 6η, while those in the kinetic energy dissipation field are more topologically complex and range in scale from 1η to 10η. The mean sizes of scalar and kinetic energy dissipative structures are 3η and 4η, respectively. The constant Λ relating mean scalar dissipative structure size to outer scale variables ( ) is measured to be 7.8. These results indicate that scalar dissipative structures are approximately a factor of two smaller than has been suggested in previous studies. 2 / 1 4 / 3 D Sc Re − − δ δ Λ = λ † Graduate Student, Student Member AIAA ‡ Associate Professor, Senior Member AIAA Copyright © by M. S. Tsurikov and N. T. Clemens. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.