Shape effects on turbulent modulation by large nearly neutrally buoyant particles

Gabriele Bellani, Margaret L. Byron, Audric G. Collignon, Colin R. Meyer, Evan A. Variano

Research output: Contribution to journalArticle

63 Citations (Scopus)

Abstract

We investigate dilute suspensions of Taylor-microscale-sized particles in homogeneous isotropic turbulence. In particular, we focus on the effect of particle shape on particle-fluid interaction. We conduct laboratory experiments using a novel experimental technique to simultaneously measure the kinematics of fluid and particle phases. This uses transparent particles having the same refractive index as water, whose motion we track via embedded optical tracers. We compare the turbulent statistics of a single-phase flow to the turbulent statistics of the fluid phase in a particle-laden suspension. Two suspensions are compared, one in which the particles are spheres and the other in which they are prolate ellipsoids with aspect ratio 2. We find that spherical particles at volume fraction Øv = 0. 14% reduce the turbulent kinetic energy (TKE) by 15 % relative to the single-phase flow. At the same volume fraction (and slightly smaller total surface area), ellipsoidal particles have a much smaller effect: they reduce the TKE by 3 % relative to the single-phase flow. Spectral analysis shows the details of TKE reduction and redistribution across spatial scales: spherical particles remove energy from large scales and reinsert it at small scales, while ellipsoids remove relatively less TKE from large scales and reinsert relatively more at small scales. Shape effects are far less evident in the statistics of particle rotation, which are very similar for ellipsoids and spheres. Comparing these with fluid enstrophy statistics, we find that particle rotation is dominated by velocity gradients on scales much larger than the particle characteristic length scales.

Original languageEnglish (US)
Pages (from-to)41-60
Number of pages20
JournalJournal of Fluid Mechanics
Volume712
DOIs
StatePublished - Dec 10 2012

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Kinetic energy
Modulation
Statistics
modulation
Fluids
Volume fraction
single-phase flow
ellipsoids
kinetic energy
statistics
Spectrum analysis
Aspect ratio
Refractive index
Kinematics
Turbulence
fluids
Water
homogeneous turbulence
isotropic turbulence
Experiments

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Bellani, Gabriele ; Byron, Margaret L. ; Collignon, Audric G. ; Meyer, Colin R. ; Variano, Evan A. / Shape effects on turbulent modulation by large nearly neutrally buoyant particles. In: Journal of Fluid Mechanics. 2012 ; Vol. 712. pp. 41-60.
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Shape effects on turbulent modulation by large nearly neutrally buoyant particles. / Bellani, Gabriele; Byron, Margaret L.; Collignon, Audric G.; Meyer, Colin R.; Variano, Evan A.

In: Journal of Fluid Mechanics, Vol. 712, 10.12.2012, p. 41-60.

Research output: Contribution to journalArticle

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