Analysis of turbulent flow structures in the straight rectangular open channel with floating vegetated islands.
Coherent vortex structures
Floating vegetated islands
Quadrant analysis
Spectral analysis
Journal
Environmental science and pollution research international
ISSN: 1614-7499
Titre abrégé: Environ Sci Pollut Res Int
Pays: Germany
ID NLM: 9441769
Informations de publication
Date de publication:
Jul 2020
Jul 2020
Historique:
received:
05
02
2020
accepted:
27
04
2020
pubmed:
8
5
2020
medline:
11
7
2020
entrez:
8
5
2020
Statut:
ppublish
Résumé
Floating vegetated islands (FVIs) are extensively implemented in various river ecology restoration projects, given their capability of decontaminating pollutants. The fluid dynamical behaviors of turbulence through FVIs are studied in the flume by using the SonTek Acoustic Doppler Velocimetry. Through conventional spectral and quadrant analyses, flow characteristics, such as energy content and turbulent momentum exchange, are investigated as the flow encountered a series of root canopies. A shear layer with corresponding coherent vortex structures at the bottom of root canopies occurred, which is generated by Kelvin-Helmholtz instabilities. These instabilities are usually derived from velocity differences between root canopy and gap region. Shear- and stem-scale vortices are identified by using spectral analysis. The power spectral density function on measured vertical velocity fluctuations in the flow direction near the bottom of root canopies from the leading edge of FVIs is computed. Given the flow developing downstream, a series of the spectral curves has gradually showed one dominant dimensionless frequency at 0.046. The sweep and ejection events have contributed prominently to the Reynolds stress in whole vertical direction. Momentum flux carried by sweeps outweighs its counterpart carried by ejections inside root canopies. However, the situation is different outside root canopies. The sweep-ejection contributions are brief but crucial to the total turbulent momentum exchange, which is in good agreement with considerable studies on turbulent flow through canopies.
Identifiants
pubmed: 32378110
doi: 10.1007/s11356-020-09087-3
pii: 10.1007/s11356-020-09087-3
doi:
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
26856-26867Subventions
Organisme : National Natural Science Foundation of China
ID : 11872285
Organisme : National Natural Science Foundation of China
ID : 11672213
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