Circulation in turbulent flow through a contraction

Vivek Mugundhan, Sigurdur T. Thoroddsen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We study experimentally the statistical properties and evolution of circulation in a turbulent flow passing through a smooth 2-D contraction. The turbulence is generated with active grids to reach (Formula presented.) at the inlet to the 2.5:1 contraction. We employ time-resolved 3-D Lagrangian Particle Tracking technique with the Shake-The-Box algorithm to obtain volumetric velocity fields which we use to calculate the simultaneous circulation in three perpendicular planes. Forming a circulation vector and studying the PDFs of the relative strength of its components, we can quantify how the mean strain enhances and orients coherent vortical structures with the streamwise direction. This is further studied with streamwise space and time correlations of the circulations over a range of loop sizes. The streamwise component of the circulation, over same-size square loops, shows increased integral length, while the other two components are less affected. The circulation around the compressive direction weakens and reaches prominent negative correlation values, suggesting buckling or sharp reorientation of transverse vortices. The PDFs of circulation transit from non-Gaussian to Gaussian behaviour as the loop size is increased from dissipative to large scales.

Original languageEnglish (US)
Pages (from-to)577-612
Number of pages36
JournalJournal of Turbulence
Volume24
Issue number11-12
DOIs
StatePublished - 2023

Keywords

  • active grid
  • circulation
  • coherent structures
  • Contraction
  • grid turbulence
  • Lagrangian Particle Tracking
  • Shake-The-Box
  • strained turbulence

ASJC Scopus subject areas

  • Computational Mechanics
  • Condensed Matter Physics
  • Mechanics of Materials
  • General Physics and Astronomy

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