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Experiments in Fluids

, 54:1500 | Cite as

Defining the roughness sublayer and its turbulence statistics

  • Emma Florens
  • Olivier EiffEmail author
  • Frédéric Moulin
Research Article

Abstract

The roughness sublayer in a turbulent open-channel flow over a very rough wall is investigated experimentally both within the canopy and above using particle image velocimetry by gaining complete optical access with new methodologies without disturbing the flow. This enabled reliable estimates of the double-averaged mean and turbulence profiles to be obtained by minimizing and quantifying the usual errors introduced by limited temporal and spatial sampling. It is shown, for example, that poor spatial sampling can lead to erroneous vertical profiles in the roughness sublayer. Then, in order to better define and determine the roughness sublayer height, a methodology based on the measured spatial dispersion is proposed which takes into account temporal sampling errors. The results reveal values well below the usual more ad hoc estimates for all statistics. Finally, the double-averaged mean and turbulence statistics in the roughness sublayer are discussed.

Keywords

Particle Image Velocimetry Particle Image Velocimetry Measurement Roughness Element Spatial Dispersion Spatial Inhomogeneity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

This work was partially supported by Hydralab IV project funded by the European Commission (Grant Number 261520). Help in conceiving and setting up the optical experiments is gratefully acknowledged to S. Cazin and E. Cid.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Institut de Mécanique des Fluides de ToulouseUniversité de Toulouse, INPT, UPS; CNRSToulouseFrance

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