Features of velocity distribution and secondary flow in compound channel with vegetation

s: In riverine, marsh, coastal, and other environments, vegetation communities are widely distributed and interact with the flow system to produce more complicated flow structures. Four sets of indoor flume vegetation flow experiments were conducted using a typical Beach trough structure in the lower sections of the Yangtze River as an example. The compound channel was divided into the main channel zone, side slope zone, and side beach zone, and simulated vegetation such as reed, sedge, and dwarf grass was used. The emphasis was on the hydrodynamic properties under semi-covered submerged rigid vegetation and semi-covered non-submerged rigid vegetation. This research focuses on the Shiono and Knight equations (SKM model) to clarify the distribution characteristics of cross-section flow velocity and the "equivalent diameter D" of gradual vegetation in water. We also propose a new secondary flow model using a genetic algorithm and investigate the relationship between the parameters of the vegetation the flow structure and the distribution pattern of the secondary flow coefficient values. Finally, it employs the Taylor method to demonstrate that the proposed "equivalent diameter D" of the vegetation has some value within a reasonable threshold range. Eventually, the depth-averaged velocity of the compound channel was accurately predicted by combining the experimental data with the novel SKM model. The proposed model can provide technical support for river flooding.