### Abstract

This paper investigates the drag exerted by randomly distributed, rigid, emergent circular cylinders of uniform diameter d. Laboratory measurements are presented for solid volume fraction phi=0.091, 0.15, 0.20, 0.27, and 0.35 and cylinder Reynolds number Re-p U(p)d/nu=25 to 685, where U-p=temporally and cross-sectionally averaged pore velocity and nu=kinematic viscosity. These ranges coincide with conditions in aquatic plant canopies. The temporally and cross-sectionally averaged drag coefficient, C-D, decreased with increasing Re-p and increased with increasing phi under the flow conditions investigated. The dimensionless ratio of the mean drag per unit cylinder length <(f(D)) over bar >(H) to the product of the viscosity, mu, and U-p exhibits a linear Re-p dependence of the form <(f(D)) over bar >(H)/(mu U-p)=alpha(0)+alpha Re-1(p), consistent with Ergun's formulation for packed columns. In the range of experimental conditions, alpha(1), increases monotonically with phi. In contrast, alpha(0) is constant within uncertainty for 0.15 <= phi <= 0.35, which suggests that viscous drag per unit cylinder length is independent of phi in this range.

Original language | English |
---|---|

Pages (from-to) | 34-41 |

Number of pages | 8 |

Journal | Journal of Hydraulic Engineering |

Volume | 134 |

Issue number | 1 |

DOIs | |

Publication status | Published - Jan 2008 |

### Keywords

- vegetation
- drag
- aquatic plants
- two-dimensional flow
- open channel flow
- experimental data
- cylinders

### Cite this

**Laboratory investigation of mean drag in a random array of rigid, emergent cylinders.** / Tanino, Yukie; Nepf, Heidi M.

Research output: Contribution to journal › Article

*Journal of Hydraulic Engineering*, vol. 134, no. 1, pp. 34-41. https://doi.org/10.1061/(ASCE)0733-9429(2008)134:1(34)

}

TY - JOUR

T1 - Laboratory investigation of mean drag in a random array of rigid, emergent cylinders

AU - Tanino, Yukie

AU - Nepf, Heidi M.

PY - 2008/1

Y1 - 2008/1

N2 - This paper investigates the drag exerted by randomly distributed, rigid, emergent circular cylinders of uniform diameter d. Laboratory measurements are presented for solid volume fraction phi=0.091, 0.15, 0.20, 0.27, and 0.35 and cylinder Reynolds number Re-p U(p)d/nu=25 to 685, where U-p=temporally and cross-sectionally averaged pore velocity and nu=kinematic viscosity. These ranges coincide with conditions in aquatic plant canopies. The temporally and cross-sectionally averaged drag coefficient, C-D, decreased with increasing Re-p and increased with increasing phi under the flow conditions investigated. The dimensionless ratio of the mean drag per unit cylinder length <(f(D)) over bar >(H) to the product of the viscosity, mu, and U-p exhibits a linear Re-p dependence of the form <(f(D)) over bar >(H)/(mu U-p)=alpha(0)+alpha Re-1(p), consistent with Ergun's formulation for packed columns. In the range of experimental conditions, alpha(1), increases monotonically with phi. In contrast, alpha(0) is constant within uncertainty for 0.15 <= phi <= 0.35, which suggests that viscous drag per unit cylinder length is independent of phi in this range.

AB - This paper investigates the drag exerted by randomly distributed, rigid, emergent circular cylinders of uniform diameter d. Laboratory measurements are presented for solid volume fraction phi=0.091, 0.15, 0.20, 0.27, and 0.35 and cylinder Reynolds number Re-p U(p)d/nu=25 to 685, where U-p=temporally and cross-sectionally averaged pore velocity and nu=kinematic viscosity. These ranges coincide with conditions in aquatic plant canopies. The temporally and cross-sectionally averaged drag coefficient, C-D, decreased with increasing Re-p and increased with increasing phi under the flow conditions investigated. The dimensionless ratio of the mean drag per unit cylinder length <(f(D)) over bar >(H) to the product of the viscosity, mu, and U-p exhibits a linear Re-p dependence of the form <(f(D)) over bar >(H)/(mu U-p)=alpha(0)+alpha Re-1(p), consistent with Ergun's formulation for packed columns. In the range of experimental conditions, alpha(1), increases monotonically with phi. In contrast, alpha(0) is constant within uncertainty for 0.15 <= phi <= 0.35, which suggests that viscous drag per unit cylinder length is independent of phi in this range.

KW - vegetation

KW - drag

KW - aquatic plants

KW - two-dimensional flow

KW - open channel flow

KW - experimental data

KW - cylinders

U2 - 10.1061/(ASCE)0733-9429(2008)134:1(34)

DO - 10.1061/(ASCE)0733-9429(2008)134:1(34)

M3 - Article

VL - 134

SP - 34

EP - 41

JO - Journal of Hydraulic Engineering

JF - Journal of Hydraulic Engineering

SN - 0733-9429

IS - 1

ER -