3D Current-induced Local Scour around Dumbbell-Shaped Steel Suspending Cofferdams
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摘要: 为研究跨海桥梁施工过程中围堰周围海床的局部冲刷深度与冲刷坑形态，运用有限差分软件Flow-3D建立了水流作用下哑铃型围堰周围海床冲刷的三维数值模型.对新建模型的精度进行了验证，基于此模型研究了哑铃型围堰周围的流场特征及吃水深度、流速对围堰周围海床局部冲刷深度的影响.研究结果表明：受围堰与钢护筒影响，围堰周围流场特征比较紊乱；随着吃水深度与流速的增加，哑铃型围堰周围海床的冲刷深度逐渐增大，当吃水深度为12.88 m，流速大小为4 m/s时，围堰周围最大冲刷深度接近8 m，然而与流速相比，吃水深度对哑铃型围堰周围海床冲刷深度的影响相对较小，围堰吃水深度由6.88 m增加到15.88 m时，最大冲刷深度增加不超过25%；最大冲刷深度发生在靠近围堰中心线的钢护筒附近；冲刷坑平面形态与围堰形状类似，围堰周围海床冲刷范围受流速影响较大，而受围堰吃水深度影响较小.Abstract: To investigate the local scour around a cofferdam, a three-dimensional numerical model for current-induced sediment scour around a dumbbell-shaped steel suspending cofferdam was established. After its validation using previous experimental data, the proposed model was applied to explore the local scour around dumbbell-shaped steel suspending cofferdams under various conditions. The numerical results indicate that the flow field distribution around the cofferdam is very complex owing to the mutual influence of the cofferdam and the steel casings. In addition, the maximum scour depth occurs around the casing adjacent to the centreline of the cofferdam, which increases with increasing current velocity and draught; the scour plain patterns are similar to the shape of the cofferdam. The results of this study can provide new evidence for studies of soil stability, and can also provide a reference for predicting the scour pattern around coastal structures.
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Key words:
- current velocity /
- cofferdams /
- scour /
- CFD
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图 7 围堰周围海床局部冲刷模型
Figure 7. Profile of the scour model around the dumbbell-shaped steel suspending cofferdam
图 8 不同网格密度下围堰周围海床最大冲刷深度
Figure 8. Maximum scour depths around the cofferdam with various mesh systems
图 9 围堰及钢护筒周围流速矢量分布
Figure 9. Velocity vector field around the dumbbell-shaped steel suspending cofferdam and the steel casings
图 10 围堰及钢护筒周围流线分布
Figure 10. Streamlines around the dumbbell-shaped steel suspending cofferdam and the steel casings
图 11 不同吃水深度下围堰周围最大冲刷深度
Figure 11. Variations in the maximum scour depth with the submerged depth of the cofferdam
图 13 不同流速下哑铃型围堰周围海床冲刷形态立面图
Figure 13. Elevation of scour patterns around the dumbbell-shaped steel suspending cofferdam at various velocities
表 1 不同流场位置网格尺寸分布
Table 1. Mesh size in different regions of the flow field
沿x方向流场位置/m 0~260 260~400 400~500 网格尺寸/m 2.0 0.5 2.0 
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表 2 数值案例所取参数
Table 2. Parameters used in numerical examples
名称 数值 水流速度/(m·s-1) 1.0或2.0或3.0 水深/m 26.5 海床厚度/m 10 围堰吃水深度/m 12.88 围堰高度/m 16 围堰在水流方向尺寸/m 37.8 围堰在垂直水流方向尺寸/m 84.8 钢护筒在水流方向间距/m 8.2 钢护筒在垂直水流方向间距/m 8.2 钢护筒半径/m 2.8 泥沙平均粒径/m 0.006 9 床面倾斜角/(°) 31 泥沙密度/(kg·m-3) 2 650
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