Turbulent flow structure at a discordant river confluence: Asymmetric jet dynamics with implications for channel morphology
Turbulent flow structure at a discordant river confluence: Asymmetric jet dynamics with implications for channel morphology
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DOI：
10.1002/2016jf004126
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发表时间：
2017-06
期刊：
影响因子：
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通讯作者：
A. Sukhodolov;J. Krick;T. Sukhodolova;Zhen Cheng;B. Rhoads;G. Constantinescu
中科院分区：
文献类型：
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作者：
A. Sukhodolov;J. Krick;T. Sukhodolova;Zhen Cheng;B. Rhoads;G. Constantinescu
只有少数现场研究对非协调交汇处的湍流结构进行了研究；这种交汇处的流动动力学主要是在实验室中进行的。本文报道了非协调河流交汇处湍流结构的现场研究结果。这些结果支持了流速比大于2的非协调冲积交汇处的流动呈现喷流特征的假设。标度分析表明，射流核心区的动力学特性与自由射流十分相似，但汇流区复杂的流动结构对射流的扩散有很强的局部抑制或增强作用。这种喷流行为对这些类型的汇合处的地貌动力学过程具有重要的意义。在这个不协调的交汇处，喷流的高能核心被从河床上移开，从而抑制了冲刷；然而，螺旋运动在喷流附近发展，特别是在高流量时，这可能会促进冲刷。数值实验表明，支流入口处沉积楔的存在或不存在会强烈地影响射流从床上的脱离和汇流区内射流的角度。
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.