Large-scale structures of scalar and velocity in a turbulent jet flow

Jesse Reijtenbagh, Jerry Westerweel, Willem Van De Water*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

We study the relation between large-scale structures in the concentration field with those in the velocity field in a dye-seeded turbulent jet. The scalar concentration in a plane is measured using laser-induced fluorescence. Uniform concentration zones of an advected scalar are indentified using cluster analysis. We simultaneously measure the two-dimensional velocity field using particle image velocimetry. The structures in the velocity field are characterized by finite-time Lyapunov exponents. The measurement of the scalar- and velocity fields moves with the mean flow. In this moving frame, turbulent structures remain in focus long enough to observe well-defined ridges of the finite-time Lyapunov field. This field gauges the rate of point separation along Lagrangian trajectories; it was measured both for future and past times since the instant of observation. The edges of uniform concentration zones are correlated with the ridges of the past-time Lyapunov field, but not with those of the future-time Lyapunov field. We quantify this relation using both conditional averages and the ordinary correlation function.

Original languageEnglish
Article number084611
Number of pages11
JournalPhysical Review Fluids
Volume6
Issue number8
DOIs
Publication statusPublished - 2021

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