Experiments in Fluids

, Volume 41, Issue 6, pp 857–867 | Cite as

Measurements of turbulence characteristics in an open-channel flow over a transitionally-rough bed using particle image velocimetry

Research Article

Abstract

The particle image velocimetry technique was used to measure characteristics of a turbulent flow over a transitionally-rough fixed bed in an open-channel flow. These conditions are typical of flows encountered in sediment transport problems. Measurements obtained with this technique were used to investigate the distributions of velocities, turbulence intensities, Reynolds stress, and third- and fourth-order moments in a region above y + = 10. The present results are in good agreement to those previously obtained on smooth walls and provide further evidence that PIV can be applied successfully to investigate turbulence in open-channel flows over a rough bed.

List of symbols

Dv, Du

turbulent diffusion coefficients in streamwise and wall-normal directions

Fk

vertical flux of turbulent kinetic energy

Fu, Fv

flatness factors for streamwise and wall-normal velocity components

ks

roughness height (m)

ks+

roughness Reynolds number, u * k s

Re

Reynolds number, Uh

Re*

Reynolds number, u * h

S

channel slope (m/m)

Su, Sv

skewness factors for the streamwise and wall-normal velocity components

u

mean streamwise velocity (m/s)

u*

shear velocity (m/s)

u+

dimensionless velocity, u/u *

u′, v′, w

velocity fluctuation in streamwise, wall-normal and transverse directions

urms, vrms

velocity standard deviation in streamwise and wall-normal directions

urms+

turbulence intensity in streamwise direction, \({u_{\rm rms}}\mathord{\left/ {\vphantom {{u_{\rm rms}} {u_\ast}}} \right.\kern-\nulldelimiterspace} {u_\ast }\)

vrms+

turbulence intensity in wall-normal directions, \({v_{\rm rms}} \mathord{\left/ {\vphantom {{v_{\rm rms}} {u_\ast}}} \right.\kern-\nulldelimiterspace} {u_\ast}\)

 −〈u+v+

dimensionless Reynolds shear stress, \(-\overline {u'v'}/u_\ast ^2\)

y+

dimensionless wall-normal axis, yu *

ΔU+

shift in the log-law due to roughness

Notes

Acknowledgments

This research was supported by the Coastal Geosciences Program of the US Office of Naval Research, with grants N00014-01-1-0337 and N00014-01-1-0540 (DURIP).

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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  1. 1.Laboratoire de Mécanique des Fluides et d’AcoustiqueUMR CNRS 5509VilleurbanneFrance
  2. 2.Departamento de Ingenieria CivilUniversidad de ChileSantiagoChile
  3. 3.Department of Civil and Environmental Engineering, V.T. Chow Hydrosystems LaboratoryUniversity of IllinoisUrbanaUSA

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