Finite-sized rigid spheres in turbulent Taylor-Couette flow: Effect on the overall drag

Dennis Bakhuis, Ruben A. Verschoof, Varghese Mathai, Sander G. Huisman, Detlef Lohse, Chao Sun* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

3 Citations (Scopus)
34 Downloads (Pure)

Abstract

We report on the modification of drag by neutrally buoyant spherical finite-sized particles in highly turbulent Taylor-Couette (TC) flow. These particles are used to disentangle the effects of size, deformability and volume fraction on the drag, and are contrasted to the drag in bubbly TC flow. From global torque measurements, we find that rigid spheres hardly decrease or increase the torque needed to drive the system. The size of the particles under investigation has a marginal effect on the drag, with smaller diameter particles showing only slightly lower drag. Increase of the particle volume fraction shows a net drag increase. However, this increase is much smaller than can be explained by the increase in apparent viscosity due to the particles. The increase in drag for increasing particle volume fraction is corroborated by performing laser Doppler anemometry, where we find that the turbulent velocity fluctuations also increase with increasing volume fraction. In contrast to rigid spheres, for bubbles, the effective drag reduction also increases with increasing Reynolds number. Bubbles are also much more effective in reducing the overall drag.

Original languageEnglish
Pages (from-to)246-261
Number of pages16
JournalJournal of fluid mechanics
Volume850
DOIs
Publication statusPublished - 4 Jul 2018

Keywords

  • UT-Hybrid-D
  • Multiphase flow
  • Shear layer turbulence
  • Drag reduction

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