Numerical study of the effects of vegetation stem thickness on the flow characteristics of curved channels

A curved channel is a common flow form in nature, often hosting aquatic vegetation along rivers. The stem thickness of this vegetation affects its resistance to flow and subsequently influences flow characteristics. To explore the impact of stem thickness on river flow in curved channels, we developed a Reynolds stress model based on real river flow conditions and vegetation data. The flow characteristics were analyzed in terms of flow velocity, Reynolds stress and turbulence intensity by varying the stem thickness of the vegetation in the vegetated area. The results of the study reveal that: (1) Water velocity in the vegetated area is significantly reduced compared to the non-vegetated area, with a greater reduction observed for thicker stems. Increasing the vegetation diameter by 3 mm resulted in a velocity decrease of 2.31–26.55%. (2) Thicker vegetation stems lead to more intense energy exchange in water flow. A 3 mm increase in vegetation diameter increased Reynolds stress by 91.81–139.70%. (3) Turbulent kinetic energy in the vegetated area is significantly higher than in the non-vegetated area, with greater turbulence intensity observed for thicker vegetation stems. Increasing the vegetation diameter by 3 mm resulted in a turbulent kinetic energy increase of 115.19–218.55%.