Three-Dimensional Hydrodynamic Analysis and Early Warning of Ω-Collapse in the Lower Reaches of the Yangtze River Based on Experimental Study on Generalized Model

AbstractUnder the background of the construction of cascade reservoir group in the main stream of the Yangtze River, the lower reaches of the Yangtze River are faced with new water and sediment situation, which leads to the increased risk of bank collapse in the lower reaches of the Yangtze River. Therefore, the purpose of this study is to have a certain supporting significance for the prevention and control of riverbank collapse disasters. The study takes the Jiangsu section of the lower reaches of the Yangtze River as the research object. Firstly, according to the measured data over the years, the macroscopic characteristics of the collapsed bank in the Jiangsu section are analyzed, and the temporal and spatial distribution characteristics are mainly analyzed. The research results show that the collapse of the Jiangsu section of the Yangtze River is dominated by Ω-collapse, which mostly occurs in the flood season and the post-flood receding water period. The frequency of bank collapse in the Yangzhong Reach is relatively the highest among all river segments, and there are more bank collapses on the north bank than the south bank. According to statistics, the average collapse width of the collapse in the Jiangsu section can reach 130 m, the depth of the collapse can reach 60 m, and the ratio of the average bank collapse to the depth can reach 2.15. Then, aiming at the characteristics of the main bank collapse type in the Jiangsu section is the Ω-collapse, the experimental investigation and numerical calculation are used to conduct in-depth research, combined with the measured data, probability and statistical analysis and theoretical analysis. Three-dimensional hydrodynamic analysis is carried out on the mainstream area near the collapse area and outside the collapse area, focusing on the analysis of its nearshore velocity and shear stress and other factors. Combined with the water tank test, the water flow in the inner surface, middle and bottom layers of the Ω-type nest was studied under different flow levels, and it was concluded that the water flow in the nest had a counterclockwise backflow, and the backflow intensity gradually weakened from the side wall to the center. And the phenomenon that the surface layer and the bottom water flow are separated, and this phenomenon becomes more prominent with the increase of the flow rate.