Flow structure within a vegetation patch in a gravel-bed river

Investigation of the interactions between submerged vegetation patch and flow structure is of crucial importance for river engineering. Most of hydraulic models have been presented for fully developed flows over uniform vegetation in the laboratory conditions; however, the mentioned interactions are...

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Published inJournal of Hydrology and Hydromechanics Vol. 67; no. 2; pp. 154 - 162
Main Authors Jahadi, Mahsa, Afzalimehr, Hossein, Rowinski, Paweł M.
Format Journal Article
LanguageEnglish
Published Bratislava Sciendo 01.06.2019
De Gruyter Poland
Subjects
Evolution
Flow structures
Gravel
Gravel bed river
Hydraulic models
Mathematical models
Mixed layer
Mixing layer
Profiles
River engineering
River flow
Rivers
Spatially evolving flow
Submerged plants
Submerged vegetation patch
Vegetation
Velocity distribution
Velocity profiles
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Summary:Investigation of the interactions between submerged vegetation patch and flow structure is of crucial importance for river engineering. Most of hydraulic models have been presented for fully developed flows over uniform vegetation in the laboratory conditions; however, the mentioned interactions are complex in river flows where the flow is not developed along small patch. This reveals a gap between developed and non-developed flow along the vegetation patch. This study was conducted in a gravel-bed river in the central Iran. The results reveal that the flow structure in evolving flow (non-developed flow) along the patch resembles that in shallow mixing layer. Accordingly, a shallow mixing layer model and modified equations are combined to quantify evolving area along the patch. The evolving shallow mixing layer equations for the flow along a non-uniform vegetation patch reach a reasonable agreement with field data. However, the spreading coefficient of this model less than one was reported in literature, 0.06 and 0.12. In addition, the flow immediately downstream the vegetation patch behaves similar to a jet and is parameterized by two conventional models, conventional logarithmic law and mixing layer theory. These models present a reasonable agreement with the measured velocity profiles immediately downstream the patch.
ISSN:0042-790X
0042-790X
1338-4333
DOI:10.2478/johh-2019-0001