Theory for flow resistance caused by submerged roughness elements

Research output: Contribution to journalArticleAcademicpeer-review

13 Citations (Scopus)

Abstract

Herein, a phenomenological theory that unifies the flow resistance caused by a variety of submerged bluff bodies, including cylindrical vegetation, two-dimensional dunes and the roughness elements studied in Schlichting's 1936 experiments, is presented. For the different flow obstructions, scaling relations that relate the equivalent roughness length to the obstructions’ spatial dimensions are derived, by adopting the concepts of the turbulent energy cascade and the momentum thickness in the wake of a bluff body. In the derivation, it is hypothesized that the equivalent roughness height represents the volumetric average of the prevailing turbulence length scale that is present in wakes of the roughness elements. A comparison with experimental literature data indicates that the derived scaling relations capture the dominant dependencies of the equivalent roughness length. These expressions have important engineering applications in large-scale flows where employment of more detailed flow-modelling techniques is not feasible.
Original languageEnglish
Pages (from-to)10-17
JournalJournal of hydraulic research
Volume50
Issue number1
DOIs
Publication statusPublished - 2012

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roughness
Surface roughness
submerged body
flow modeling
dune
momentum
Momentum
Turbulence
turbulence
engineering
vegetation
energy
experiment
Experiments

Keywords

  • IR-81664
  • Hydraulic roughness
  • Flow resistance
  • METIS-287182
  • Scaling
  • Vegetation
  • Dunes

Cite this

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abstract = "Herein, a phenomenological theory that unifies the flow resistance caused by a variety of submerged bluff bodies, including cylindrical vegetation, two-dimensional dunes and the roughness elements studied in Schlichting's 1936 experiments, is presented. For the different flow obstructions, scaling relations that relate the equivalent roughness length to the obstructions’ spatial dimensions are derived, by adopting the concepts of the turbulent energy cascade and the momentum thickness in the wake of a bluff body. In the derivation, it is hypothesized that the equivalent roughness height represents the volumetric average of the prevailing turbulence length scale that is present in wakes of the roughness elements. A comparison with experimental literature data indicates that the derived scaling relations capture the dominant dependencies of the equivalent roughness length. These expressions have important engineering applications in large-scale flows where employment of more detailed flow-modelling techniques is not feasible.",
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Theory for flow resistance caused by submerged roughness elements. / Huthoff, Freek.

In: Journal of hydraulic research, Vol. 50, No. 1, 2012, p. 10-17.

Research output: Contribution to journalArticleAcademicpeer-review

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T1 - Theory for flow resistance caused by submerged roughness elements

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PY - 2012

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AB - Herein, a phenomenological theory that unifies the flow resistance caused by a variety of submerged bluff bodies, including cylindrical vegetation, two-dimensional dunes and the roughness elements studied in Schlichting's 1936 experiments, is presented. For the different flow obstructions, scaling relations that relate the equivalent roughness length to the obstructions’ spatial dimensions are derived, by adopting the concepts of the turbulent energy cascade and the momentum thickness in the wake of a bluff body. In the derivation, it is hypothesized that the equivalent roughness height represents the volumetric average of the prevailing turbulence length scale that is present in wakes of the roughness elements. A comparison with experimental literature data indicates that the derived scaling relations capture the dominant dependencies of the equivalent roughness length. These expressions have important engineering applications in large-scale flows where employment of more detailed flow-modelling techniques is not feasible.

KW - IR-81664

KW - Hydraulic roughness

KW - Flow resistance

KW - METIS-287182

KW - Scaling

KW - Vegetation

KW - Dunes

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