Structure of flow over alluvial bedforms: An experiment on linking field and laboratory methods

Alexander N. Sukhodolov, Juan J. Fedele, Bruce L Rhoads

Research output: Contribution to journalArticlepeer-review

Abstract

This paper presents results of a field study designed to examine the structure of flow over mobile and fixed bedforms in a natural stream and to compare the results with findings of previous laboratory studies within the framework of double time-space averaging approach. Measurements of turbulence were obtained in a small river in Illinois, USA, over a fine spatial grid of sampling points above a mobile sandy bedform and its artificially moulded replica. Flow structure over the artificial bedform is similar to that observed in laboratory studies, but is markedly different from the flow structure over natural bedforms. These differences are most pronounced in the roughness sublayer, whereas flow in the logarithmic layer over natural and artificial sand waves is fairly similar and exhibits spatial uniformity. The double time-space averaged distributions of turbulence statistics conform to the multilayer model of flow structure over bedforms. Mean velocity distributions indicate neither classical flow recirculation nor substantial reduction of velocities in the lee of bedform crests. However, vertical patterns of turbulence statistics over depth suggest that stacked wakes similar to those observed in laboratory studies exist above the bedforms. Thus, despite the absence of flow separation, wake development seems to be induced by the systematic influence of upstream bedforms on the vertical structure of turbulence.

Original languageEnglish (US)
Pages (from-to)1292-1310
Number of pages19
JournalEarth Surface Processes and Landforms
Volume31
Issue number10
DOIs
StatePublished - Sep 1 2006

Keywords

  • Bedforms
  • Double time-space averaging
  • River turbulence
  • Turbulent stresses

ASJC Scopus subject areas

  • Geography, Planning and Development
  • Earth-Surface Processes
  • Earth and Planetary Sciences (miscellaneous)

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