Lock-in regions of laminar flows over a streamwise oscillating circular cylinder

Ki Ha Kim, Jung-il Choi

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

In this paper, flow over a streamwise oscillating circular cylinder is numerically simulated to examine the effects of the driving amplitude and frequency on the distribution of the lock-in regions in laminar flows. At , lock-in is categorized according to the spectral features of the lift coefficient as two different lock-in phenomena: Harmonic and subharmonic lock-in. These lock-in phenomena are represented as maps on the driving amplitude-frequency plane, which have subharmonic lock-in regions and two harmonic lock-in regions. The frequency range of the subharmonic region is shifted to lower frequencies with increasing amplitude, and the lower boundary of this subharmonic region is successfully predicted. A symmetric harmonic region with a symmetric vortex pattern is observed in a certain velocity range for a moving cylinder. Aerodynamic features induced by different flow patterns in each region are presented on the driving amplitude-frequency plane. The lock-in region and aerodynamic features at and are compared with the results for . A subharmonic region and two harmonic regions are observed at , and these show the same features as for at a low driving amplitude. Lock-in at also shows one subharmonic region and two harmonic regions. However, compared with the case, the symmetric harmonic lock-in is dominant. The features of aerodynamic force at and are represented on a force map, which shows similar characteristics in corresponding regions for the case.

Original languageEnglish
Pages (from-to)315-351
Number of pages37
JournalJournal of Fluid Mechanics
Volume858
DOIs
Publication statusPublished - 2019 Jan 10

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circular cylinders
Circular cylinders
laminar flow
Laminar flow
Aerodynamics
harmonics
Flow patterns
Vortex flow
aerodynamics
lift coefficients
aerodynamic forces
flow distribution
frequency ranges
vortices
low frequencies

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

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title = "Lock-in regions of laminar flows over a streamwise oscillating circular cylinder",
abstract = "In this paper, flow over a streamwise oscillating circular cylinder is numerically simulated to examine the effects of the driving amplitude and frequency on the distribution of the lock-in regions in laminar flows. At , lock-in is categorized according to the spectral features of the lift coefficient as two different lock-in phenomena: Harmonic and subharmonic lock-in. These lock-in phenomena are represented as maps on the driving amplitude-frequency plane, which have subharmonic lock-in regions and two harmonic lock-in regions. The frequency range of the subharmonic region is shifted to lower frequencies with increasing amplitude, and the lower boundary of this subharmonic region is successfully predicted. A symmetric harmonic region with a symmetric vortex pattern is observed in a certain velocity range for a moving cylinder. Aerodynamic features induced by different flow patterns in each region are presented on the driving amplitude-frequency plane. The lock-in region and aerodynamic features at and are compared with the results for . A subharmonic region and two harmonic regions are observed at , and these show the same features as for at a low driving amplitude. Lock-in at also shows one subharmonic region and two harmonic regions. However, compared with the case, the symmetric harmonic lock-in is dominant. The features of aerodynamic force at and are represented on a force map, which shows similar characteristics in corresponding regions for the case.",
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Lock-in regions of laminar flows over a streamwise oscillating circular cylinder. / Kim, Ki Ha; Choi, Jung-il.

In: Journal of Fluid Mechanics, Vol. 858, 10.01.2019, p. 315-351.

Research output: Contribution to journalArticle

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AB - In this paper, flow over a streamwise oscillating circular cylinder is numerically simulated to examine the effects of the driving amplitude and frequency on the distribution of the lock-in regions in laminar flows. At , lock-in is categorized according to the spectral features of the lift coefficient as two different lock-in phenomena: Harmonic and subharmonic lock-in. These lock-in phenomena are represented as maps on the driving amplitude-frequency plane, which have subharmonic lock-in regions and two harmonic lock-in regions. The frequency range of the subharmonic region is shifted to lower frequencies with increasing amplitude, and the lower boundary of this subharmonic region is successfully predicted. A symmetric harmonic region with a symmetric vortex pattern is observed in a certain velocity range for a moving cylinder. Aerodynamic features induced by different flow patterns in each region are presented on the driving amplitude-frequency plane. The lock-in region and aerodynamic features at and are compared with the results for . A subharmonic region and two harmonic regions are observed at , and these show the same features as for at a low driving amplitude. Lock-in at also shows one subharmonic region and two harmonic regions. However, compared with the case, the symmetric harmonic lock-in is dominant. The features of aerodynamic force at and are represented on a force map, which shows similar characteristics in corresponding regions for the case.

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