Depth-averaged flow in presence of submerged cylindrical elements

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The hydraulic resistance of vegetation can play a major role in the hydrodynamics of rivers with extensive natural floodplains. Vegetation penetrates the flow field and thereby causes drag that, in addition to the flow resistance at the bed level, causes energy losses and slows down the flow. Here, these flow processes are studied in an idealized form by treating vegetation as cylindrical roughness elements with homogeneous geometrical dimensions. Based on scaling considerations of the forces involved, depth-averaged flow velocities within the resistance layer and in the free flowing layer above the roughness elements are estimated. This yields a new description of the overall average flow field, which is entirely determined by measurable geometrical boundaries. We tested the new relation against laboratory flume experiments and found very good agreement (R2 =0.98). The new description even showed realistic results when the depth of flow is of similar size as the height of the roughness elements themselves. This result demonstrates its superiority over commonly used wall-roughness methods.
Original languageUndefined
Title of host publicationProceedings of Riverflow 2006 - Third International Conference on Fluvial Hydraulics, 6-8 September 2006, Lissabon , Portugal
EditorsRui M.L. Ferreira
Place of PublicationLisbon, Portugal
PublisherTaylor & Francis
ISBN (Print)9780415408158
Publication statusPublished - 6 Sept 2006
EventRiver Flow 2006: 3rd International Conference on Fluvial Hydraulics - Lisbon, Portugal
Duration: 6 Sept 20068 Sept 2006
Conference number: 3

Publication series

PublisherTaylor & Francis


ConferenceRiver Flow 2006


  • METIS-230610
  • IR-60436

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