### Abstract

Shear-free turbulence generated from an oscillating grid in a water tank impinging on an impermeable surface at varying Reynolds number 74 ≤ R e l ≤ 570 was studied experimentally, where the Reynolds number is defined based on the root-mean-square (r.m.s) horizontal velocity and the integral length scale. A particular focus was paid to the turbulence characteristics for low R e l < 150 to investigate the minimum limit of R e l obeying the profiles of rapid distortion theory. The measurements taken at near base included the r.m.s turbulent velocities, evolution of isotropy, integral length scales, and energy spectra. Statistical analysis of the velocity data showed that the anisotropic turbulence structure follows the theory for flows with R e l ≥ 117. At low R e l < 117, however, the turbulence profile deviated from the prediction where no amplification of horizontal velocity components was observed and the vertical velocity components were seen to be constant towards the tank base. Both velocity components sharply decreased towards zero at a distance of ≈ 1/3 of the integral length scale above the base due to viscous damping. The lower limit where R e l obeys the standard profile was found to be within the range 114 ≤ R e l ≤ 116.

Original language | English |
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Article number | 683537 |

Journal | Scientific World Journal |

Volume | 2014 |

DOIs | |

Publication status | Published - 2014 |

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### ASJC Scopus subject areas

- Biochemistry, Genetics and Molecular Biology(all)
- Environmental Science(all)
- Medicine(all)

### Cite this

*Scientific World Journal*,

*2014*, [683537]. https://doi.org/10.1155/2014/683537

**Characteristics of Low Reynolds Number Shear-Free Turbulence at an Impermeable Base.** / Wan Mohtar, Wan Hanna Melini; Elshafie, A.

Research output: Contribution to journal › Article

*Scientific World Journal*, vol. 2014, 683537. https://doi.org/10.1155/2014/683537

}

TY - JOUR

T1 - Characteristics of Low Reynolds Number Shear-Free Turbulence at an Impermeable Base

AU - Wan Mohtar, Wan Hanna Melini

AU - Elshafie, A.

PY - 2014

Y1 - 2014

N2 - Shear-free turbulence generated from an oscillating grid in a water tank impinging on an impermeable surface at varying Reynolds number 74 ≤ R e l ≤ 570 was studied experimentally, where the Reynolds number is defined based on the root-mean-square (r.m.s) horizontal velocity and the integral length scale. A particular focus was paid to the turbulence characteristics for low R e l < 150 to investigate the minimum limit of R e l obeying the profiles of rapid distortion theory. The measurements taken at near base included the r.m.s turbulent velocities, evolution of isotropy, integral length scales, and energy spectra. Statistical analysis of the velocity data showed that the anisotropic turbulence structure follows the theory for flows with R e l ≥ 117. At low R e l < 117, however, the turbulence profile deviated from the prediction where no amplification of horizontal velocity components was observed and the vertical velocity components were seen to be constant towards the tank base. Both velocity components sharply decreased towards zero at a distance of ≈ 1/3 of the integral length scale above the base due to viscous damping. The lower limit where R e l obeys the standard profile was found to be within the range 114 ≤ R e l ≤ 116.

AB - Shear-free turbulence generated from an oscillating grid in a water tank impinging on an impermeable surface at varying Reynolds number 74 ≤ R e l ≤ 570 was studied experimentally, where the Reynolds number is defined based on the root-mean-square (r.m.s) horizontal velocity and the integral length scale. A particular focus was paid to the turbulence characteristics for low R e l < 150 to investigate the minimum limit of R e l obeying the profiles of rapid distortion theory. The measurements taken at near base included the r.m.s turbulent velocities, evolution of isotropy, integral length scales, and energy spectra. Statistical analysis of the velocity data showed that the anisotropic turbulence structure follows the theory for flows with R e l ≥ 117. At low R e l < 117, however, the turbulence profile deviated from the prediction where no amplification of horizontal velocity components was observed and the vertical velocity components were seen to be constant towards the tank base. Both velocity components sharply decreased towards zero at a distance of ≈ 1/3 of the integral length scale above the base due to viscous damping. The lower limit where R e l obeys the standard profile was found to be within the range 114 ≤ R e l ≤ 116.

UR - http://www.scopus.com/inward/record.url?scp=84933055159&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84933055159&partnerID=8YFLogxK

U2 - 10.1155/2014/683537

DO - 10.1155/2014/683537

M3 - Article

C2 - 25250384

AN - SCOPUS:84933055159

VL - 2014

JO - Scientific World Journal

JF - Scientific World Journal

SN - 2356-6140

M1 - 683537

ER -