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

doi:10.11988/ckyyb.20240532

Abstract

Abstract:

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.

Key words: river bend slope protection, ecological protection, sand and gravel rip-rap bag, geometric modeling of curved riverbed, CFD-DPM method, protection effect

CLC Number:

TV851疏浚(河床整理)

SUN Hong-guang, HONG Liang-zhen, WANG Mao-mei, WANG Lian. Protective Effects of Different Shapes of Ecological Rip-rap Bags Based on CFD-DPM Model[J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(4): 19-26.

Figures/Tables 15

Fig.1 CFD-DPM coupling calculation flow

Fig.2 Topography of the river channel of Baguazhou section of the Yangtze River

Fig.3 Arrangement of baffles on the bottom surface

Fig.4 River bend revetment model

Table 1 Model parameters

模型参数	参数值	模型参数	参数值
颗粒直径颗粒密度	D=0.3 mm ρ=2 600 kg/m³	流体密度	ρ=1 000 kg/m³
粒子喷射速度	0 m/s	入口流体流速	v=0.5 m/s
喷射粒子流量	0.01 g/s	重力加速度	g=10 m/s²

Fig.5 Volume meshing in different revetment modes

Table 2 Maximum size for mesh independence validation

种类	网格最大尺寸/mm	种类	网格最大尺寸/mm
A	12	D	6.45
B	10	E	6
C	8	F	4

Fig.6 Mesh independence validation results

Fig.7 Velocity contours at cross section 1 mm from the riverbed bottom in different revetment modes

Fig.8 Pressure contours on lateral and bottom surfaces of the riverbank under different revetment modes

Fig.9 Velocity of particles under different revetment modes

Fig.10 Sampling arrangement in the revetment mode with hemispherical bags

Fig.11 Statistics on the amount of blocked sediment in different revetment modes

Fig.12 Number and trajectories of particles detected on the wall

Fig.13 Reynolds number of sediment particles under different revetment modes

[1]	GU Xiang-yi, DOU Zi-ning. Innovative Mechanism of Judicial Cooperation for Ecological Environmental Governance in the Yangtze River Basin [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(2): 9-15.
[2]	XU Yong-xin, QI Ji-hong. Protection and Restoration of Ecological Environment from Perspectives of China and Africa [J]. Journal of Changjiang River Scientific Research Institute, 2022, 39(3): 1-7.
[3]	SUN Hui, LIU Jun, HU Bo, ZHANG Quan. Effect of Cement-modified Expansive Soil in Slope Protection [J]. Journal of Changjiang River Scientific Research Institute, 2017, 34(5): 53-57.
[4]	YANG Yue-shu, XIA Zhen-yao, XIAO Hai, JIA Feng-gang, HU Mo-zhen, DENG Li. Experimental Research on Shear Strength ofIndigofera amblyantha Root-Soil Composite [J]. Journal of Changjiang River Scientific Research Institute, 2014, 31(4): 72-76.
[5]	YANG Yue-shu, XIA Zhen-yao, XIAO Hai, ZHOU Shi, WU Bin, YANG Xiao-feng. Application of System Engineering Principles to Slope Ecological Protection Project [J]. Journal of Changjiang River Scientific Research Institute, 2013, 30(10): 32-36.