Oscillating-grid turbulence at large strokes: Revisiting the equation of Hopfinger and Toly

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

A quasi-isotropic, quasi-homogeneous turbulence generated by an oscillating-grid, spatially decays according to power law of u ∝Z-nu, where u is the root mean square (rms) horizontal velocity, Z is the vertical distance from the grid and nu = 1. However, the findings of Nokes and Yi indicate that as the stroke of oscillation increases, the power law nu ≠ 1 and does not follow the established decay law equation of Hopfinger. This paper investigates the characteristics of the turbulence that are generated using larger strokes S/M 1.6 and 2 and compares with that obtained using a S/M = 0.8, which is the stroke used when the equation was developed. Measurements of the grid-generated turbulence in a water tank were taken using particle image velocimetry (PIV). The results showed that the homogeneity occurred at distance beyond 2.5 mesh spacings away from the grid midplane, independent of the stroke and the frequency of oscillation. Within this region, the turbulent kinetic energy distribution was quasi-homogeneous, and the secondary mean flow is negligible. The statistical characteristics of the measured turbulence confirmed that although nu decreases as stroke increases, the grid-turbulence generated at S/M 1.6 and 2 obeys the universal decay law.

Original languageEnglish
Pages (from-to)473-481
Number of pages9
JournalJournal of Hydrodynamics
Volume28
Issue number3
DOIs
Publication statusPublished - 1 Jun 2016

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strokes
Stroke
Turbulence
turbulence
grids
Grid
Decay
Power Law
decay
Oscillation
homogeneous turbulence
Water tanks
oscillations
Energy Distribution
particle image velocimetry
Kinetic energy
Homogeneity
Velocity measurement
Mean Square
Spacing

Keywords

  • decay power law
  • large strokes
  • oscillating-grid turbulence

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanical Engineering
  • Mechanics of Materials
  • Modelling and Simulation

Cite this

Oscillating-grid turbulence at large strokes : Revisiting the equation of Hopfinger and Toly. / Wan Mohtar, Wan Hanna Melini.

In: Journal of Hydrodynamics, Vol. 28, No. 3, 01.06.2016, p. 473-481.

Research output: Contribution to journalArticle

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