Lu, H.; Gu, F.; Qi, D.; Chen, X., and Wang, Y., 2019. Investigating near-bottom hydrodynamic processes in the Yangtze River estuary using in situ measurements. Journal of Coastal Research, 35(4), 805–813. Coconut Creek (Florida), ISSN 0749-0208.
This study aimed to investigate the characteristics of hydrodynamic processes in the near-bottom layer of the Yangtze River estuary to further understand near-bottom hydrodynamic processes in this area. For this purpose, in situ acoustic Doppler velocimetry measurements were taken at two sites (upstream and downstream) during a neap-spring tidal cycle. Results show that tidal asymmetry is significant with wide variations across different areas. The turbulence is anisotropic, and the turbulence pulsation intensity increases with current speed, while turbulence anisotropy weakens. Cd values estimated at both sites vary from 10–4 to 10–2, exhibiting obvious time variation and relationship with current. Their average values are 0.001 and 0.0008, respectively, which are much smaller than 0.0061, which is associated with the local median grain size of bed sediments. The relationship between inertial dissipation rate (εsp) and friction velocity (u*) at both sites agrees well with the values using the classical law of the wall most of the time, indicating that the classical law of the wall is applicable to the near-bottom of the Yangtze estuary most of the time, except when current speed is low. Differences in the dynamic processes between TR1 and TR2 indicate that, apart from the tidal influence and the geographical location influence, stratification should be another important factor driving hydrodynamic processes in the near-bottom layer.
