[Back]

S. Deng, J. Xia, M. Zhou, Z. Li, G. Duan, J. Shen, K. Blanckaert:
"Secondary Flow and Flow Redistribution in Two Sharp Bends on the Middle Yangtze River";
Water Resources Research, 57 (2021), e2020WR028534.

It remains an open question whether the state of knowledge on bend hydrodynamics
applies to sharp bends in the largest river systems on Earth. This paper reports a field investigation into
the hydrodynamics in two consecutive sharp bends of the Middle Yangtze River (MYR), and demonstrates
that the reduced-order model of Blanckaert and de Vriend is able to resolve the secondary flow strength
and continuous flow redistribution in rivers of this size to high accuracy. Consequently, the model has
been validated over the entire range of scales. These two bends show similarities to those of smaller
size in terms of bathymetry, flow redistribution, and secondary flow evolution. The transverse location
of the core of maximum velocity along the bends lags behind the thalweg by approximately half a
width. A center-region cell of secondary flow develops over the outer bank near the apex, and gradually
decays downstream until it completely vanishes at the bend exit. Both bends are mildly curved from the
perspective of hydrodynamic modeling, with a weak interaction between the secondary flow and primary
flow, although they are sharply curved from the perspective of geomorphology (width/radius > 0.5).
A term-by-term analysis of the model indicates that the flow redistribution is primarily controlled by
planimetric changes in curvature and by topographic steering, and is slightly influenced by the secondary
flow. However, the secondary flow may indirectly affect the flow redistribution by conditioning the bed
topography. Important knowledge gaps remain with respect to the coupling between the hydrodynamic
and morphological processes.

http://dx.doi.org/10.1029/2020WR028534