Author(s): Guanghui Yan; Saiyu Yuan
Linked Author(s): Saiyu Yuan
Keywords: River confluence; Tributary floodplain; Hydrodynamic characteristics; Secondary flows
Abstract: The confluence of rivers is a key node that controls the movement of water and sediment and changes in the aquatic ecological environment in the watershed. In the world’s major river basins such as the Yangtze River Basin and the Amazon Basin, it is common for tributaries to intersect with the main stream in a compound channel shape, and the floodplains of tributaries are submerged during the flood season and exposed during the dry season. However, the current understanding of the hydrodynamic characteristics of the intersection under the influence of tidal flats is still insufficient. By conducting detailed water tank experiments and numerical simulations, the three-dimensional velocity field, turbulent kinetic energy, separation zone, and secondary flow at the intersection under the influence of tidal flats were analyzed in detail. The experimental results indicate that under the influence of the shoal, larger scale and stronger secondary flow movements, inclined shear layers, and additional high-speed zones appear at the intersection, which are related to flow separation at the shoal platform and high momentum flow in the tributaries. In addition, based on the Reynolds stress turbulence model, the influence of eight different characteristics on the flow structure at the intersection of compound channels was studied; The discovery of tributary shoals greatly enhances the intensity and size of secondary flow, and the position of secondary flow depends on the height and width of the shoals; The width of the separation zone increases with the increase of the width and height of the branch shoal, which is because the shoal restricts the cross section of the branch and enhances the momentum of the branch water flow. However, when the width of the shoal exceeds half of the width of the branch, the width of the separation zone increases but the length decreases. Large scale secondary flow can damage the downstream separation zone and cause local water surface rise. The research results have enriched our understanding of the hydrodynamic characteristics at intersections, and are also of great significance for flood management and ecological restoration.
Year: 2024