### Abstract

The physical structures of velocity are examined from a recent direct numerical simulation of fully developed incompressible turbulent pipe flow (Wu, Baltzer & Adrian, J. Fluid Mech., vol. 698, 2012, pp. 235-281) at a Reynolds number of Re_{D} = 240580 (based on bulk velocity) and a Kármán number of R^{+} = 685. In that work, the periodic domain length of 30 pipe radii R was found to be sufficient to examine long motions of negative streamwise velocity fluctuation that are commonly observed in wall-bounded turbulent flows and correspond to the large fractions of energy present at very long streamwise wavelengths (≥3R). In this paper we study how long motions are composed of smaller motions. We characterize the spatial arrangements of very large-scale motions (VLSMs) extending through the logarithmic layer and above, and we find that they possess dominant helix angles (azimuthal inclinations relative to streamwise) that are revealed by two-and three-dimensional two-point spatial correlations of velocity. The correlations also reveal that the shorter, large-scale motions (LSMs) that concatenate to comprise the VLSMs are themselves more streamwise aligned. We show that the largest VLSMs possess a form similar to roll cells centred above the logarithmic layer and that they appear to play an important role in organizing the flow, while themselves contributing only a minor fraction of the flow turbulent kinetic energy. The roll cell motions play an important role with the smaller scales of motion that are necessary to create the strong streamwise streaks of low-velocity fluctuation that characterize the flow.

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

Pages (from-to) | 236-279 |

Number of pages | 44 |

Journal | Journal of Fluid Mechanics |

Volume | 720 |

DOIs | |

State | Published - Apr 2013 |

### Fingerprint

### Keywords

- turbulent boundary layers
- turbulent flows

### ASJC Scopus subject areas

- Mechanical Engineering
- Mechanics of Materials
- Condensed Matter Physics

### Cite this

*Journal of Fluid Mechanics*,

*720*, 236-279. https://doi.org/10.1017/jfm.2012.642

**Structural organization of large and very large scales in turbulent pipe flow simulation.** / Baltzer, J. R.; Adrian, Ronald; Wu, Xiaohua.

Research output: Contribution to journal › Article

*Journal of Fluid Mechanics*, vol. 720, pp. 236-279. https://doi.org/10.1017/jfm.2012.642

}

TY - JOUR

T1 - Structural organization of large and very large scales in turbulent pipe flow simulation

AU - Baltzer, J. R.

AU - Adrian, Ronald

AU - Wu, Xiaohua

PY - 2013/4

Y1 - 2013/4

N2 - The physical structures of velocity are examined from a recent direct numerical simulation of fully developed incompressible turbulent pipe flow (Wu, Baltzer & Adrian, J. Fluid Mech., vol. 698, 2012, pp. 235-281) at a Reynolds number of ReD = 240580 (based on bulk velocity) and a Kármán number of R+ = 685. In that work, the periodic domain length of 30 pipe radii R was found to be sufficient to examine long motions of negative streamwise velocity fluctuation that are commonly observed in wall-bounded turbulent flows and correspond to the large fractions of energy present at very long streamwise wavelengths (≥3R). In this paper we study how long motions are composed of smaller motions. We characterize the spatial arrangements of very large-scale motions (VLSMs) extending through the logarithmic layer and above, and we find that they possess dominant helix angles (azimuthal inclinations relative to streamwise) that are revealed by two-and three-dimensional two-point spatial correlations of velocity. The correlations also reveal that the shorter, large-scale motions (LSMs) that concatenate to comprise the VLSMs are themselves more streamwise aligned. We show that the largest VLSMs possess a form similar to roll cells centred above the logarithmic layer and that they appear to play an important role in organizing the flow, while themselves contributing only a minor fraction of the flow turbulent kinetic energy. The roll cell motions play an important role with the smaller scales of motion that are necessary to create the strong streamwise streaks of low-velocity fluctuation that characterize the flow.

AB - The physical structures of velocity are examined from a recent direct numerical simulation of fully developed incompressible turbulent pipe flow (Wu, Baltzer & Adrian, J. Fluid Mech., vol. 698, 2012, pp. 235-281) at a Reynolds number of ReD = 240580 (based on bulk velocity) and a Kármán number of R+ = 685. In that work, the periodic domain length of 30 pipe radii R was found to be sufficient to examine long motions of negative streamwise velocity fluctuation that are commonly observed in wall-bounded turbulent flows and correspond to the large fractions of energy present at very long streamwise wavelengths (≥3R). In this paper we study how long motions are composed of smaller motions. We characterize the spatial arrangements of very large-scale motions (VLSMs) extending through the logarithmic layer and above, and we find that they possess dominant helix angles (azimuthal inclinations relative to streamwise) that are revealed by two-and three-dimensional two-point spatial correlations of velocity. The correlations also reveal that the shorter, large-scale motions (LSMs) that concatenate to comprise the VLSMs are themselves more streamwise aligned. We show that the largest VLSMs possess a form similar to roll cells centred above the logarithmic layer and that they appear to play an important role in organizing the flow, while themselves contributing only a minor fraction of the flow turbulent kinetic energy. The roll cell motions play an important role with the smaller scales of motion that are necessary to create the strong streamwise streaks of low-velocity fluctuation that characterize the flow.

KW - turbulent boundary layers

KW - turbulent flows

UR - http://www.scopus.com/inward/record.url?scp=84875017821&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84875017821&partnerID=8YFLogxK

U2 - 10.1017/jfm.2012.642

DO - 10.1017/jfm.2012.642

M3 - Article

AN - SCOPUS:84875017821

VL - 720

SP - 236

EP - 279

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

SN - 0022-1120

ER -