### Abstract

The structure of velocity in the outer region of turbulent channel flow (y^{+} ≳ 100) is examined statistically to determine the average flow field associated with spanwise vortical motions. Particle image velocimetry measurements of the streamwise and wall-normal velocity components are correlated with a vortex marker (swirling strength) in the streamwise-wall-normal plane, and linear stochastic estimation is used to estimate the conditional average of the two-dimensional velocity field associated with a swirling motion. The mean structure consists of a series of swirling motions located along a line inclined at 12°-13° from the wall. The pattern is consistent with the observations of outer-layer wall turbulence in which groups of hairpin vortices occur aligned in the streamwise direction. While the observational evidence for the aforementioned model was based upon both experimental and computational visualization of instantaneous structures, the present results show that, on average, the instantaneous structures occur with sufficient frequency, strength, and order to leave an imprint on the statistics of the flow as well. Results at Re_{τ} = 547 and 1734 are presented.

Original language | English (US) |
---|---|

Pages (from-to) | 433-443 |

Number of pages | 11 |

Journal | Journal of Fluid Mechanics |

Volume | 431 |

DOIs | |

State | Published - Mar 25 2001 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Mechanics of Materials
- Computational Mechanics
- Physics and Astronomy(all)
- Condensed Matter Physics

### Cite this

*Journal of Fluid Mechanics*,

*431*, 433-443. https://doi.org/10.1017/S0022112001003512

**Statistical evidence of hairpin vortex packets in wall turbulence.** / Christensen, K. T.; Adrian, Ronald.

Research output: Contribution to journal › Article

*Journal of Fluid Mechanics*, vol. 431, pp. 433-443. https://doi.org/10.1017/S0022112001003512

}

TY - JOUR

T1 - Statistical evidence of hairpin vortex packets in wall turbulence

AU - Christensen, K. T.

AU - Adrian, Ronald

PY - 2001/3/25

Y1 - 2001/3/25

N2 - The structure of velocity in the outer region of turbulent channel flow (y+ ≳ 100) is examined statistically to determine the average flow field associated with spanwise vortical motions. Particle image velocimetry measurements of the streamwise and wall-normal velocity components are correlated with a vortex marker (swirling strength) in the streamwise-wall-normal plane, and linear stochastic estimation is used to estimate the conditional average of the two-dimensional velocity field associated with a swirling motion. The mean structure consists of a series of swirling motions located along a line inclined at 12°-13° from the wall. The pattern is consistent with the observations of outer-layer wall turbulence in which groups of hairpin vortices occur aligned in the streamwise direction. While the observational evidence for the aforementioned model was based upon both experimental and computational visualization of instantaneous structures, the present results show that, on average, the instantaneous structures occur with sufficient frequency, strength, and order to leave an imprint on the statistics of the flow as well. Results at Reτ = 547 and 1734 are presented.

AB - The structure of velocity in the outer region of turbulent channel flow (y+ ≳ 100) is examined statistically to determine the average flow field associated with spanwise vortical motions. Particle image velocimetry measurements of the streamwise and wall-normal velocity components are correlated with a vortex marker (swirling strength) in the streamwise-wall-normal plane, and linear stochastic estimation is used to estimate the conditional average of the two-dimensional velocity field associated with a swirling motion. The mean structure consists of a series of swirling motions located along a line inclined at 12°-13° from the wall. The pattern is consistent with the observations of outer-layer wall turbulence in which groups of hairpin vortices occur aligned in the streamwise direction. While the observational evidence for the aforementioned model was based upon both experimental and computational visualization of instantaneous structures, the present results show that, on average, the instantaneous structures occur with sufficient frequency, strength, and order to leave an imprint on the statistics of the flow as well. Results at Reτ = 547 and 1734 are presented.

UR - http://www.scopus.com/inward/record.url?scp=0035946224&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035946224&partnerID=8YFLogxK

U2 - 10.1017/S0022112001003512

DO - 10.1017/S0022112001003512

M3 - Article

AN - SCOPUS:0035946224

VL - 431

SP - 433

EP - 443

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

SN - 0022-1120

ER -