Turbulent flow structure at a discordant river confluence: Asymmetric jet dynamics with implications for channel morphology

Alexander N Sukhodolov; Julian Krick; Tatiana A Sukhodolova; Zhengyang Cheng; Bruce L Rhoads; George S Constantinescu

doi:10.1002/2016JF004126

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Turbulent flow structure at a discordant river confluence: Asymmetric jet dynamics with implications for channel morphology

Journal article

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Turbulent flow structure at a discordant river confluence: Asymmetric jet dynamics with implications for channel morphology

Alexander N Sukhodolov, Julian Krick, Tatiana A Sukhodolova, Zhengyang Cheng, Bruce L Rhoads and George S Constantinescu

Journal of geophysical research. Earth surface, Vol.122(6), pp.1278-1293

06/2017

DOI: 10.1002/2016JF004126

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Abstract

Only a handful of field studies have examined turbulent flow structure at discordant confluences; the dynamics of flow at such confluences have mainly been examined in the laboratory. This paper reports results of a field‐based investigation of turbulent flow structure at a discordant river confluence. These results support the hypothesis that flow at a discordant alluvial confluence with a velocity ratio greater than 2 exhibits jet‐like characteristics. Scaling analysis shows that the dynamics of the jet core are quite similar to those of free jets but that the complex structure of flow at the confluence imposes strong effects that can locally suppress or enhance the spreading rate of the jet. This jet‐like behavior of the flow has important implications for morphodynamic processes at these types of confluences. The highly energetic core of the jet at this discordant confluence is displaced away from the riverbed, thereby inhibiting scour; however, helical motion develops adjacent to the jet, particularly at high flows, which may promote scour. Numerical experiments demonstrate that the presence or absence of a depositional wedge at the mouth of the tributary can strongly influence detachment of the jet from the bed and the angle of the jet within the confluence. Key Points This study supports the hypothesis that flow at a discordant confluence with a velocity ratio greater than 2 exhibits jet‐like characteristics Although the dynamics of the jet core are similar to free jets, effects imposed by complex structure of ambient flow locally suppress or enhance the spreading rate of the jet This jet‐like behavior of the flow has important implications for the morphodynamic processes at such confluences

depositional wedge

discordant channel

field research

river confluence

scour

turbulent jet

Details

Title: Subtitle: Turbulent flow structure at a discordant river confluence: Asymmetric jet dynamics with implications for channel morphology
Creators: Alexander N Sukhodolov - Leibniz Association
Julian Krick - GEO Morphix Ltd Burlington Ontario Canada
Tatiana A Sukhodolova - Leibniz Association
Zhengyang Cheng - University of Iowa
Bruce L Rhoads - University of Illinois at Urbana–Champaign
George S Constantinescu - University of Iowa
Resource Type: Journal article
Publication Details: Journal of geophysical research. Earth surface, Vol.122(6), pp.1278-1293
DOI: 10.1002/2016JF004126
ISSN: 2169-9003
eISSN: 2169-9011
Number of pages: 16
Grant note: Deutsche Forschungsgemeinschaft (DFG) (SU 405/7‐1) US National Science Foundation (1359911) BCS Geography and Spatial Sciences Program of the US National Science Foundation (1359836; 1359911) Deutsche Forschungsgemainschaft (SU 405/7‐1; SU 405/4‐1) US National Science Foundation (1359836)
Language: English
Date published: 06/2017
Academic Unit: Civil and Environmental Engineering
Record Identifier: 9984197316502771

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