Coherent structures and turbulent molecular mixing in gaseous planar shear layers

T. R. Meyer, J Craig Dutton, R. P. Lucht

Research output: Contribution to journalArticlepeer-review

Abstract

Quantitative planar visualization of molecular mixing dynamics in large- and intermediate-scale coherent structures is reported for the first time in the developing and far-field regions of gaseous planar shear layers. A dual-tracer (nitric oxide and acetone) planar laser-induced fluorescence (PLIF) technique is implemented as the gaseous analogue to acid/base chemical reactions that have previously been used to study molecular mixing in liquid shear layers. Data on low-speed, high-speed, and total molecularly mixed fluid fractions are collected for low- to high-speed velocity ratios from 0.25 to 0.44 and Reynolds numbers, Reδ from 18 600 to 103 000. Within this range of conditions, mixed-fluid probability density functions and ensemble-averaged statistics are highly influenced by the homogenizing effect of large-scale Kelvin-Helmholtz rollers and the competing action of intermediate-scale secondary instabilities. Small-scale turbulence leads to near-unity mixing efficiencies and mixed-fluid probabilities within the shear layer, with subresolution stirring being detected primarily along the interface with free-stream fluid. Current molecular-mixing data compare favourably with previous time-averaged probe-based measurements while providing new insight on the effects of coherent structures, velocity ratio, downstream distance, and differences between low- and high-speed fluid entrainment.

Original languageEnglish (US)
Pages (from-to)179-205
Number of pages27
JournalJournal of Fluid Mechanics
Volume558
DOIs
StatePublished - Jul 10 2006

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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