Macro-turbulent flows (i.e., coherent flow structures reaching through the whole water column), have not been studied widely in northern seasonally frozen rivers during both open-channel and ice-covered flow conditions. Thus, we aim: (1) to detect and compare the macro-turbulent flow, both at open-channel and ice-covered flow conditions; (2) to explore spatial variation of macro-turbulent flow characteristics within a meander bend; and (3) to detect the effects of near-bed layer velocity fluctuation on bedload transport during differing overall flow conditions. The analyses are based on 5–10 min-long acoustic Doppler current profiler (ADCP) measurements from a subarctic river. The ice-covered low flow, and open-channel higher and lower flow conditions were measured over the period of 2016 to 2020. This study found that macro-turbulent flow existed at all measurement locations under both open-channel and ice-covered flow conditions. Macro-turbulent flow was most consistent and obvious in the streamwise velocity component, and in particular at the inlet and outlet of the investigated meander bend. During all seasons, the near-bed velocities consistently exceeded the sufficient amount for sediment transport. At inlet and outlet areas, the greatest near-bed velocity fluctuation across the critical threshold for sediment transport coincided with the measurement times having frequent macro-turbulent flow.

中文翻译：

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冰盖和明渠条件下亚北极河流的宏观湍流及其对沉积物输送潜力的影响

宏观湍流（即，贯穿整个水体的连贯流结构）尚未在明渠和冰覆盖的流动条件下在北部季节性结冰的河流中得到广泛研究。因此，我们的目标是： (1) 在明渠和冰覆盖的流动条件下检测和比较宏观湍流；(2) 探索曲折内宏观湍流特征的空间变化；(3) 检测不同整体流动条件下近床层速度波动对床载输运的影响。分析基于来自亚北极河流的 5-10 分钟长的声学多普勒电流剖面仪 (ADCP) 测量结果。在 2016 年至 2020 年期间测量了冰覆盖的低流量和明渠高低流量条件。该研究发现，在明渠和冰覆盖的流动条件下，所有测量位置都存在宏观湍流。宏观湍流在流向速度分量中最为一致和明显，特别是在研究的曲折弯道的入口和出口处。在所有季节中，近床速度始终超过沉积物输送的足够量。在入口和出口区域，穿过沉积物输移临界阈值的最大近床速度波动与具有频繁宏观湍流的测量时间重合。特别是在所研究的曲折弯道的入口和出口处。在所有季节中，近床速度始终超过沉积物输送的足够量。在入口和出口区域，穿过沉积物输移临界阈值的最大近床速度波动与具有频繁宏观湍流的测量时间重合。特别是在所研究的曲折弯道的入口和出口处。在所有季节中，近床速度始终超过沉积物输送的足够量。在入口和出口区域，穿过沉积物输移临界阈值的最大近床速度波动与具有频繁宏观湍流的测量时间重合。