Numerical Simulation Study on Water Flow Characteristics and Motion Mechanism near a New Eco-Revetment Structure

The eco-revetment structure serves as a link for material, information, and energy exchange between rivers, bank slopes, and organisms, providing a guarantee for the stability of river ecosystems. This study designed a new type of eco-revetment structure based on its characteristics. The internal structure is designed as a cavity, with openings on the top and side walls and curved surfaces connecting the upper and lower components to ensure smooth water flow and stable bank slopes, providing living space for aquatic organisms. By establishing a three-dimensional numerical model and using large-eddy simulation as the main research method, the distribution law of hydraulic characteristics near the revetment structure is observed, and the mechanism of water flow movement is studied. This study indicates that the internal and external water flow conditions of the new ecological revetment structure are complex and exhibit significant spatial heterogeneity. When there are no plants, the flow directions inside and outside the structure are opposite, with hairpin vortices dominating the interior. The presence of plants significantly enhances turbulence intensity and Reynolds stress, resulting in smaller and more diverse vortex structures, and the formation of Karman vortex streets on the leeward side of plants. The movement characteristics of the revetment structure vary in different regions: in region C, when there are no plants, the value of (|Q2| + |Q4|)/(|Q1| + |Q3|) is greater than 1.5, and it increases to 3 when plants are present. The ratio for region B is 0.83 and 0.8, while for region A it is 1.02 and 1.17. When there are no plants, the Reynolds stress contribution in region A is uniform, region B shows a “hyperbolic” distribution, and the proportion of S2 and S4 at the top of region C increases sharply. Plants increase the contribution of the top of the region C to three to five times that of no plants. The complex water flow environment significantly changes the mechanism of water flow movement. The Reynolds stress contribution and turbulent kinetic energy fit well. The presence of plants leads to a Reynolds stress contribution and turbulent kinetic energy value that are about three times higher than without plants. When there are no plants, the turbulent structure within the structure is mainly influenced by S1 and S3, while when there are plants, S2 and S4 dominate the turbulence. This article provides a solid theoretical foundation and quantitative experimental basis for the study of nearshore water flow mechanisms in ecological revetment structures.