Protective Effects of Different Shapes of Ecological Rip-rap Bags Based on CFD-DPM Model

Curved slopes in natural river channels are highly susceptible to erosion, posing a significant challenge for river management. To address this issue, a comparative study was conducted on the protective effects of sand-and-gravel rip-rap bags of different shapes against erosion based on the concept of ecological slope protection. First, a geometric model of the curved-channel bed was constructed according to the actual river structure. Then, the CFD-DPM method was employed to analyze the bank-protection effects of rectangular, hemispherical, and semi-cylindrical bags placed on the concave bank of the curved channel. Results revealed that under a flow velocity of 0.5 m/s, among the three shapes of protection bags, rectangular bags bring about the least pressure on the concave bank, while semi-cylindrical bags obstruct the largest amount of sediment particles, leading to the smallest Reynolds number of particles and the minimum average particle velocity, 9% lower than that in the model without protection bags. In conclusion, rectangular rip-raping bags offers better protection for the adjacent concave bank, while semi-cylindrical bags provide the most effective sand-blocking function.