Spatially-averaged open-channel flow over a rough bed.

Vladimir Ivanovich Nikora, D. Goring, Ian Kenneth McEwan, G. Griffiths

Research output: Contribution to journalArticlepeer-review

427 Citations (Scopus)


In this paper it is suggested that the double-averaged (in temporal and in spatial domains) momentum equations should be used as a natural basis for the hydraulics of rough-bed open-channel flows, especially with small relative submergence. The relationships for the vertical distribution of the total stress for the simplest case of 2D, steady, uniform. spatially averaged flow over a rough bed with flat free surface are derived. These relationships explicitly include the form-induced stresses and form drag as components of the total stress. Using this approach, we define three types of rough-bed flows: (1) Flow with high relative submergence; (2) how with small relative submergence; and (3) flow over a partially inundated rough bed. The relationships for the double-averaged velocity distribution and hydraulic resistance for all three flow types are derived and compared with measurements where possible. The double-averaged turbulent and form-induced intensities and stresses for the case of regular spherical-segment-type roughness show the dominant role of the double-averaged turbulence stresses and form drag in momentum transfer in the near-bed region.

Original languageEnglish
Pages (from-to)123-133
Number of pages10
JournalJournal of Hydraulic Engineering
Issue number2
Publication statusPublished - Feb 2001




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