Scalar/velocity imaging of the fine scales in gas-phase turbulent jets

Abstract

Results are reported for an experimental study that is directed at investigating the fine scale structure of turbulent jet flows using the simultaneous imaging of the velocity and conserved scalar 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 fluid. The measurements resolve the classical Kolmogorov scale of the flow. These highlyresolved measurements are used to investigate the statistics of kinematic quantities such as vorticity, strain rate, and kinetic energy dissipation. They also permit the analysis of the relationships between strain, kinetic energy dissipation, and scalar dissipation. Worsening the resolution from 1 to 2 Kolmogorov scales appears to have a significant effect on the statistics of vorticity, strain, and kinetic energy dissipation, but this is believed to be due to differences in the noise present in the images rather than to a resolution effect. As further evidence for this, no significant difference is observed when the resolution is worsened from 2 to 4 Kolmogorov scales. Qualitatively, regions of high scalar dissipation tend to be correlated with regions of high principal compressive strain and high kinetic energy dissipation. The topology of the kinetic energy dissipation structures is also seen to be substantially more complex than the layer-like structures found in the scalar dissipation field. † Graduate Research Assistant, 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.