破碎波作用下圆端形桥墩受力特性数值模拟

Numerical simulation of mechanical characteristics of round ended pier impacted by breaking wave

当波浪由外海向跨海桥梁所在的近岸海域传播时,随着水深急剧变浅,波浪会发生破碎。强非线性的破碎波会给桥墩结构带来极大冲击作用。基于计算流体力学(CFD)数值软件Flow-3D建立三维数值水槽,造波边界设为斯托克斯五阶波。通过在数值水槽中建立逐渐浅化的三维地形,采用k-ω湍流模型求解雷诺平均N-S(RANS)方程,模拟破碎波冲击桥墩。与前人水槽试验及数值模拟结果进行比对,验证数值水槽的有效性。采用验证过的数值水槽,研究了不同入射波高和周期下的破碎波浪特性,计算了不同长宽比圆端形桥墩在不同入射波高的破碎波作用下受力和流场变化,讨论了最大压强作用点、准静态力和冲击力随桥墩长宽比的变化规律。研究表明:与前人试验和数值模拟相比,所建立的数值水槽具有较高精度;圆端形桥墩破波力随桥墩长宽比增大,先增大后趋于稳定,破波力峰值随着入射波高的增大而增大,同时,圆端形桥墩破波力峰值主要由冲击力控制。进行跨海桥梁圆端形桥墩设计时,应重点关注桥墩长宽比和破碎波冲击力的影响。

Wave breaks with the water depth being shallower when it propagates from the open sea to the offshore area where sea-crossing bridges are located.Strong nonlinear breaking wave will impact greatly on piers.Based on the CFD software Flow-3D,a 3D numerical flume was established,and the wave boundary created Stokes fifth order waves.Through the shoaling terrain in the numerical flume,the RANS equation was solved by k-ωturbulence model to simulate wave breaking on pier.Compared with the results of previous flume experiments and numerical simulation,the numerical flume was validated.The characteristics of breaking waves under different incident wave heights and periods were studied with the validated numerical flume.The force and flow field changes of round ended pier with different aspect ratios impacted by breaking wave under different incident wave heights were calculated.The regulations of maximum pressure point,quasi-static force and slamming force with the aspect ratio of pier were discussed.The results show that compared to previous experiments and numerical simulation,the validated flume shows high accuracy.The breaking wave force of round ended pier increases at first and then tends to be stable when pier aspect ratio enlarges.The peak gets bigger when incident wave becomes higher,and breaking wave force peak is mainly controlled by slamming force.For the design of round ended piers of sea-crossing bridges,attention should be paid to the influence of pier aspect ratio and slamming force.