### Abstract

Adverse-pressure-gradient turbulent boundary layer flow was inspected at Reynolds number based on momentum thickness, (Formula presented.), using particle image velocimetry in a refractive-index-matching flume. Proper orthogonal decomposition was used to quantify the effect of large-scale motions on the Reynolds stresses at the onset of separation and within the separated flow. Results show that approximately (Formula presented.) of the Reynolds shear stress, (Formula presented.), is due to large-scale motions containing (Formula presented.) of the turbulence kinetic energy at the tested Reynolds number. The decomposed velocity field revealed that only the first (Formula presented.) of the modes is sufficient to recover (Formula presented.) of the turbulence kinetic energy. In this partition, the large-scale motion contribution to the streamwise component of the Reynolds normal stress, (Formula presented.), is about (Formula presented.) and continues to grow with flow separation. In addition, the large- and small-scale motions equally contributed to the vertical component of the Reynolds normal stress, (Formula presented.), and the contribution of the large-scale motions increased as the flow separated. Overall, results emphasise the significant impact of the large-scale motions on the Reynolds stresses in the separated flow, which may impact flow control strategies.

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

Pages (from-to) | 563-576 |

Number of pages | 14 |

Journal | Journal of Turbulence |

Volume | 20 |

Issue number | 9 |

DOIs | |

State | Published - Sep 2 2019 |

### Fingerprint

### Keywords

- Large-scale motions
- PIV
- POD
- separation
- turbulent flow

### ASJC Scopus subject areas

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

### Cite this

*Journal of Turbulence*,

*20*(9), 563-576. https://doi.org/10.1080/14685248.2019.1683186

**On the large- and small-scale motions in a separated, turbulent-boundary-layer flow.** / Dharmarathne, Suranga; Bocanegra Evans, Humberto; Hamed, Ali M.; Aksak, Burak; Chamorro, Leonardo P.; Tutkun, Murat; Doosttalab, Ali; Castillo, Luciano.

Research output: Contribution to journal › Article

*Journal of Turbulence*, vol. 20, no. 9, pp. 563-576. https://doi.org/10.1080/14685248.2019.1683186

}

TY - JOUR

T1 - On the large- and small-scale motions in a separated, turbulent-boundary-layer flow

AU - Dharmarathne, Suranga

AU - Bocanegra Evans, Humberto

AU - Hamed, Ali M.

AU - Aksak, Burak

AU - Chamorro, Leonardo P.

AU - Tutkun, Murat

AU - Doosttalab, Ali

AU - Castillo, Luciano

PY - 2019/9/2

Y1 - 2019/9/2

N2 - Adverse-pressure-gradient turbulent boundary layer flow was inspected at Reynolds number based on momentum thickness, (Formula presented.), using particle image velocimetry in a refractive-index-matching flume. Proper orthogonal decomposition was used to quantify the effect of large-scale motions on the Reynolds stresses at the onset of separation and within the separated flow. Results show that approximately (Formula presented.) of the Reynolds shear stress, (Formula presented.), is due to large-scale motions containing (Formula presented.) of the turbulence kinetic energy at the tested Reynolds number. The decomposed velocity field revealed that only the first (Formula presented.) of the modes is sufficient to recover (Formula presented.) of the turbulence kinetic energy. In this partition, the large-scale motion contribution to the streamwise component of the Reynolds normal stress, (Formula presented.), is about (Formula presented.) and continues to grow with flow separation. In addition, the large- and small-scale motions equally contributed to the vertical component of the Reynolds normal stress, (Formula presented.), and the contribution of the large-scale motions increased as the flow separated. Overall, results emphasise the significant impact of the large-scale motions on the Reynolds stresses in the separated flow, which may impact flow control strategies.

AB - Adverse-pressure-gradient turbulent boundary layer flow was inspected at Reynolds number based on momentum thickness, (Formula presented.), using particle image velocimetry in a refractive-index-matching flume. Proper orthogonal decomposition was used to quantify the effect of large-scale motions on the Reynolds stresses at the onset of separation and within the separated flow. Results show that approximately (Formula presented.) of the Reynolds shear stress, (Formula presented.), is due to large-scale motions containing (Formula presented.) of the turbulence kinetic energy at the tested Reynolds number. The decomposed velocity field revealed that only the first (Formula presented.) of the modes is sufficient to recover (Formula presented.) of the turbulence kinetic energy. In this partition, the large-scale motion contribution to the streamwise component of the Reynolds normal stress, (Formula presented.), is about (Formula presented.) and continues to grow with flow separation. In addition, the large- and small-scale motions equally contributed to the vertical component of the Reynolds normal stress, (Formula presented.), and the contribution of the large-scale motions increased as the flow separated. Overall, results emphasise the significant impact of the large-scale motions on the Reynolds stresses in the separated flow, which may impact flow control strategies.

KW - Large-scale motions

KW - PIV

KW - POD

KW - separation

KW - turbulent flow

UR - http://www.scopus.com/inward/record.url?scp=85074851260&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85074851260&partnerID=8YFLogxK

U2 - 10.1080/14685248.2019.1683186

DO - 10.1080/14685248.2019.1683186

M3 - Article

AN - SCOPUS:85074851260

VL - 20

SP - 563

EP - 576

JO - Journal of Turbulence

JF - Journal of Turbulence

SN - 1468-5248

IS - 9

ER -