Global S&T Development Trend Analysis Platform of Resources and Environment
DOI | 10.1002/2016WR019873 |
Mixing layer and coherent structures in compound channel flows: Effects of transverse flow, velocity ratio, and vertical confinement | |
Proust, S.1; Fernandes, J. N.2; Leal, J. B.3; Riviere, N.4; Peltier, Y.5 | |
2017-04-01 | |
发表期刊 | WATER RESOURCES RESEARCH |
ISSN | 0043-1397 |
EISSN | 1944-7973 |
出版年 | 2017 |
卷号 | 53期号:4 |
文章类型 | Article |
语种 | 英语 |
国家 | France; Portugal; Norway |
英文摘要 | Turbulent mixing layers associated with streamwise uniform and nonuniform flows in compound channels (main channel with adjacent floodplains) are experimentally investigated. The experiments start with uniform flow conditions. The streamwise nonuniformity is then generated by imposing an imbalance in the upstream discharge distribution between main channel (MC) and floodplains (FPs), keeping the total discharge constant, which results in a transverse depth-averaged mean flow. This study first aims at assessing the effect of a transverse flow on the mixing layer and coherent structures that form at the MC/FP interfaces. A wide range of initial velocity ratio or dimensionless shear between MC and FP is tested. The study second aims at assessing the effect of this velocity ratio on the mixing layer, for a fixed vertical confinement of flow. The total discharge was then varied to quantify the confinement effect. The results show that, far from the inlet section, Reynolds-stresses increase with local velocity ratio for a fixed confinement and decrease with confinement for a fixed velocity ratio. It is also shown that, irrespective of confinement, the existence of quasi-two-dimensional coherent structures is driven by velocity ratio and the direction and magnitude of transverse flow. These structures cannot develop if velocity ratio is lower than 0.3 and if a strong transverse flow toward the MC occurs. In the latter case, the transverse flow is the predominant contribution to momentum exchange (compared with turbulent mixing and secondary currents), convex mean velocity profiles are observed, preventing the formation of quasi-two-dimensional structures. Plain Language Summary Owing to the numerous sources of longitudinal nonuniformity along overflowing rivers (e.g., the change in floodplain land occupation), the understanding of overbank nonuniform flows in a compound open-channel (main channel and lateral floodplains) is of primary importance. Streamwise flow nonuniformity is characterized by a transverse flow across the river. At the interface between main channel (MC) and floodplain (FP), a mixing layer populated by turbulent vortices develops. When the flow is nonuniform, the mixing layer is strongly altered. These "nonuniform mixing layers'' are encountered in several practical problems like mixing processes in rivers-e.g., sediments, nutrients, or pollutants transport from the MC to the FP-river restoration works, flood risk assessment studies. This paper presents an experimental investigation of nonuniform flows in compound channels, focusing on the mixing layer and the turbulent vortices. We assess the effects of the transverse flow on the turbulent vortices, as well as the effects of the MC/FP velocity ratio and of the vertical confinement of flow. The existence of quasi-two-dimensional vortices was found to be independent of the vertical confinement of flow (unlike uniform flows) but strongly driven by the velocity ratio and the direction and magnitude of the transverse flow. |
领域 | 资源环境 |
收录类别 | SCI-E |
WOS记录号 | WOS:000403682600048 |
WOS关键词 | 2-DIMENSIONAL TURBULENCE ; SHALLOW FLOWS ; OVERBANK FLOW ; ENERGY ; MACROVORTICES ; FLOODPLAINS |
WOS类目 | Environmental Sciences ; Limnology ; Water Resources |
WOS研究方向 | Environmental Sciences & Ecology ; Marine & Freshwater Biology ; Water Resources |
引用统计 | |
文献类型 | 期刊论文 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/21465 |
专题 | 资源环境科学 |
作者单位 | 1.IRSTEA, UR HHLY, Ctr Lyon Villeurbanne, Villeurbanne, France; 2.Natl Lab Civil Engn, Hydraul & Environm Dept, Lisbon, Portugal; 3.Univ Agder, Fac Engn & Sci, Grimstad, Norway; 4.Univ Lyon, INSA Lyon, CNRS, LMFA UMR 5509, Lyon, France; 5.UPE, EDF R&D, CEREMA, Lab Hydraul St Venant,Ecole Ponts, Chatou, France |
推荐引用方式 GB/T 7714 | Proust, S.,Fernandes, J. N.,Leal, J. B.,et al. Mixing layer and coherent structures in compound channel flows: Effects of transverse flow, velocity ratio, and vertical confinement[J]. WATER RESOURCES RESEARCH,2017,53(4). |
APA | Proust, S.,Fernandes, J. N.,Leal, J. B.,Riviere, N.,&Peltier, Y..(2017).Mixing layer and coherent structures in compound channel flows: Effects of transverse flow, velocity ratio, and vertical confinement.WATER RESOURCES RESEARCH,53(4). |
MLA | Proust, S.,et al."Mixing layer and coherent structures in compound channel flows: Effects of transverse flow, velocity ratio, and vertical confinement".WATER RESOURCES RESEARCH 53.4(2017). |
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