Author(s): Lei Xu; Saiyu Yuan; Bart Vermeulen

Linked Author(s): Saiyu Yuan, Bart Vermeulen

Keywords: River confluence; Yangtze River; Poyang Lake; Mixing interface; Flow fluctuation

Abstract: River confluences which are characterized by complex hydrodynamic conditions are the key nodes for the flood control and environment protection. Recently, flow fluctuations are increasingly being reported in the literature and are known to have important impacts on the confluence's flow field and mixing dynamics. However, the research limited to a few small-scale rivers, and no study reported its effect on velocity measurements. In the present study, a field survey was conducted at the confluence of the largest river Yangtze and the largest freshwater Poyang Lake in China in October 2022. The purposes were to investigate the flow fluctuation and its effect at a large river confluence. During the field campaign, an acoustic Doppler velocity profiling (ADCP) meter was used to monitor the water depth and three-dimensional flow velocities time series and cross section profiles. Water chemistry parameters were measured by the multi-parameter water quality meter. Preliminary results indicated the existence of the periodic fluctuation when the two flows had a significant momentum flux difference (MR = 0.01). The average velocity variation over time presented a dramatic flow fluctuation with a period of 1000 s, accompanied by alternating peaks and troughs. The time series of water quality parameter and water depth values reflect that such fluctuation may be generated by the interaction of two incoming streams. When the two streams with significant momentum differences compete for space within the confluence maybe caused the unsteadiness in the water-surface pressure-gradient field. This study provides a new understanding of the time-dependent flow structure of large-scale river confluences and provides an important reference for improving in-situ flow measurements.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p1358-cd

Year: 2023