跨海桥梁圆端形基础波流力缩尺效应研究

Scale Effects of Wave-Current Forces on Round-Ended Foundation of Sea-Crossing Bridge

为研究跨海桥梁圆端形基础在波流力作用下的缩尺效应,以西堠门公铁两用大桥圆端形基础为背景,通过流体计算软件Flow-3D模拟数值水槽,建立6种缩尺比(1∶1,1∶15,1∶25,1∶50,1∶75,1∶100)圆端形基础数值模型,基于RNG k-ε湍流模型、雷诺平均方程以及VOF自由液面捕捉法,计算各数值模型所受波流力及其周边水力特性并对比分析,并将1∶1的圆端形基础数值模型所受波流力与规范计算结果对比。结果表明:在波流作用下,圆端形基础周围会出现流速集中现象,缩尺比减小该现象不再明显,但周围流速分布特点大致相同;对于圆端形基础受到的水平波流力,1∶1模型结果小于缩尺模型结果,综合考虑峰值与谷值缩尺模型结果,建议在西堠门公铁两用大桥试验研究中采用1∶25缩尺比;依据现有规范用等效的圆形或矩形估算圆端形结构所受水平波流力,为1∶1圆端形结构数值模拟结果的1.60~1.77倍和1.49~1.70倍,据此进行设计仍可保证结构安全性。

The scale effects of wave-current forces on the round-ended foundation of the sea-crossing bridge are studied.The round-ended foundation of Xihoumen Rail-cum-Road Bridge is used as a case.In the Flow-3D software,a numerical wave flume was developed,and numerical round-ended foundations of six scales(1∶1,1∶15,1∶25,1∶50,1∶75,1∶100)were built up as well.Based on the RNG k-εturbulence model,Reynolds-averaged Navier-Stokes equations and free surface tracking method,the wave-current forces on all numerical models were calculated,the characteristics of surrounding flows were figured out.The wave-current forces on the round-ended foundation of 1∶1 scale were compared with the values given in the codes.It is shown that under the wave-current forces,there exists a flow velocity concentration surrounding the round-ended foundation,as the scale ratio decreases,the velocity concentration phenomenon becomes less significant,but the characteristics of flow velocity around different piles are roughly the same.The effects of horizontal wave-current forces on the 1∶1 model of round-ended foundation is less than on the scaled model.As per the simulation results of the models at both peak and through of waves,a 1∶25 scale model was suggested for the tests of Xihoumen Rail-cum Road Bridge.The horizontal wave-current forces on the round-ended foundation were equivalent to the calculation of round or rectangular foundations in the current codes,to the round foundations,the horizontal wave-current forces were about 1.6 to 1.77 times of the 1∶1 model of round-ended foundation,and to the rectangular foundations,the horizontal wave-current forces were about 1.49 to 1.70 times of the 1∶1 model of round-ended foundation.Referencing the codes for calculation is also able to ensure the structural safety of the round-ended foundation.