Microbubbles and Microparticles are Not Faithful Tracers of Turbulent Acceleration

Varghese Mathai, Enrico Calzavarini, Jon Brons, Chao Sun, Detlef Lohse

Research output: Contribution to journalArticleAcademicpeer-review

22 Citations (Scopus)
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Abstract

We report on the Lagrangian statistics of acceleration of small (sub-Kolmogorov) bubbles and tracer particles with Stokes number St≪1 in turbulent flow. At a decreasing Reynolds number, the bubble accelerations show deviations from that of tracer particles; i.e., they deviate from the Heisenberg-Yaglom prediction and show a quicker decorrelation despite their small size and minute St. Using direct numerical simulations, we show that these effects arise due the drift of these particles through the turbulent flow. We theoretically predict this gravity-driven effect for developed isotropic turbulence, with the ratio of Stokes to Froude number or equivalently the particle drift velocity governing the enhancement of acceleration variance and the reductions in correlation time and intermittency. Our predictions are in good agreement with experimental and numerical results. The present findings are relevant to a range of scenarios encompassing tiny bubbles and droplets that drift through the turbulent oceans and the atmosphere. They also question the common usage of microbubbles and microdroplets as tracers in turbulence research.
Original languageEnglish
Article number024501
Number of pages6
JournalPhysical review letters
Volume117
Issue number024501
DOIs
Publication statusPublished - 2016

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microparticles
tracers
bubbles
turbulent flow
Froude number
isotropic turbulence
intermittency
predictions
direct numerical simulation
Reynolds number
oceans
turbulence
statistics
gravitation
deviation
atmospheres
augmentation

Keywords

  • METIS-317170
  • IR-100763

Cite this

Mathai, Varghese ; Calzavarini, Enrico ; Brons, Jon ; Sun, Chao ; Lohse, Detlef . / Microbubbles and Microparticles are Not Faithful Tracers of Turbulent Acceleration. In: Physical review letters. 2016 ; Vol. 117, No. 024501.
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abstract = "We report on the Lagrangian statistics of acceleration of small (sub-Kolmogorov) bubbles and tracer particles with Stokes number St≪1 in turbulent flow. At a decreasing Reynolds number, the bubble accelerations show deviations from that of tracer particles; i.e., they deviate from the Heisenberg-Yaglom prediction and show a quicker decorrelation despite their small size and minute St. Using direct numerical simulations, we show that these effects arise due the drift of these particles through the turbulent flow. We theoretically predict this gravity-driven effect for developed isotropic turbulence, with the ratio of Stokes to Froude number or equivalently the particle drift velocity governing the enhancement of acceleration variance and the reductions in correlation time and intermittency. Our predictions are in good agreement with experimental and numerical results. The present findings are relevant to a range of scenarios encompassing tiny bubbles and droplets that drift through the turbulent oceans and the atmosphere. They also question the common usage of microbubbles and microdroplets as tracers in turbulence research.",
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Microbubbles and Microparticles are Not Faithful Tracers of Turbulent Acceleration. / Mathai, Varghese ; Calzavarini, Enrico; Brons, Jon; Sun, Chao ; Lohse, Detlef .

In: Physical review letters, Vol. 117, No. 024501, 024501, 2016.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Microbubbles and Microparticles are Not Faithful Tracers of Turbulent Acceleration

AU - Mathai, Varghese

AU - Calzavarini, Enrico

AU - Brons, Jon

AU - Sun, Chao

AU - Lohse, Detlef

PY - 2016

Y1 - 2016

N2 - We report on the Lagrangian statistics of acceleration of small (sub-Kolmogorov) bubbles and tracer particles with Stokes number St≪1 in turbulent flow. At a decreasing Reynolds number, the bubble accelerations show deviations from that of tracer particles; i.e., they deviate from the Heisenberg-Yaglom prediction and show a quicker decorrelation despite their small size and minute St. Using direct numerical simulations, we show that these effects arise due the drift of these particles through the turbulent flow. We theoretically predict this gravity-driven effect for developed isotropic turbulence, with the ratio of Stokes to Froude number or equivalently the particle drift velocity governing the enhancement of acceleration variance and the reductions in correlation time and intermittency. Our predictions are in good agreement with experimental and numerical results. The present findings are relevant to a range of scenarios encompassing tiny bubbles and droplets that drift through the turbulent oceans and the atmosphere. They also question the common usage of microbubbles and microdroplets as tracers in turbulence research.

AB - We report on the Lagrangian statistics of acceleration of small (sub-Kolmogorov) bubbles and tracer particles with Stokes number St≪1 in turbulent flow. At a decreasing Reynolds number, the bubble accelerations show deviations from that of tracer particles; i.e., they deviate from the Heisenberg-Yaglom prediction and show a quicker decorrelation despite their small size and minute St. Using direct numerical simulations, we show that these effects arise due the drift of these particles through the turbulent flow. We theoretically predict this gravity-driven effect for developed isotropic turbulence, with the ratio of Stokes to Froude number or equivalently the particle drift velocity governing the enhancement of acceleration variance and the reductions in correlation time and intermittency. Our predictions are in good agreement with experimental and numerical results. The present findings are relevant to a range of scenarios encompassing tiny bubbles and droplets that drift through the turbulent oceans and the atmosphere. They also question the common usage of microbubbles and microdroplets as tracers in turbulence research.

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