沉管隧道变截面管段浮运与沉放水动力特性及方案评价

Hydrodynamic characters and program evaluation of immersed tunnel with variable section during floating and sinking process

文章借助计算流体动力学(computational fluid dynamics,CFD)软件开展变截面管段浮运与沉放过程的绕流模拟,在模型试验验证的基础上,揭示管段浮运与沉放过程水流流场、压力场及涡动结构演化特征,并以此为基础,评价管段浮运和沉放方案的合理性。研究表明:CFD计算结果与模型试验结果吻合,数值模拟管段浮运可行且具备合理性;管段浮运与沉放阶段,迎水面均匀流绕流管段并加速减压,来流被挤向主流区,使水流与壁面边界层分离,在尾部形成回流区;管段表面局部出现紊流,并在壁面周围形成旋涡,涡动随流速的增加而逐渐增强。对数值计算结果进行分析,结果表明:管段沉放系泊采用的重力锚与地锚稳定性满足设计要求;管段浮运牵引及沉放系泊的钢缆拉力显著小于设计破断荷载,管段浮运与沉放钢缆方案满足强度要求。文中对管段浮运、沉放牵引钢缆方案进行了优化。

The computational fluid dynamics(CFD)simulation for flow around variable section was conducted during the floating and sinking process.The flow field,pressure field and vortex evolution characteristics were revealed based on the model test verification.On this basis,the rationality of the floating and sinking schemes of immersed section was evaluated.The study observes that CFD calculation results are consistent with those obtained from model test,which indicates that the numerical analysis is acceptable and applicable.The uniform flow around section occurs in upstream face and acceleration decompression appears during the floating and sinking process.The flow is pushed into the main area and separated from the wall surface and the backflow zone forms at the tail of the tunnel section.Turbulent flow appears locally and the vortex forms around the side wall,of which the strength increases with the increase of the velocity in a linear relation.Based on numerical calculation results,it indicates that the stability of gravity anchor and ground anchor can meet design requirements.The wire rope tension of floating traction and sinking anchoring is significantly smaller than the designed breaking load,so the wire rope scheme meets the strength requirements.Meanwhile,the wire rope scheme of the floating and sinking was optimized.