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Turbulent flow structure at a discordant river confluence: Asymmetric jet dynamics with implications for channel morphology
Author(s) -
Sukhodolov Alexander N.,
Krick Julian,
Sukhodolova Tatiana A.,
Cheng Zhengyang,
Rhoads Bruce L.,
Constantinescu George S.
Publication year - 2017
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1002/2016jf004126
Subject(s) - confluence , turbulence , jet (fluid) , morphology (biology) , channel (broadcasting) , flow (mathematics) , mechanics , geology , open channel flow , dynamics (music) , river morphology , physics , geomorphology , engineering , paleontology , computer science , programming language , sediment , acoustics , electrical engineering
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.