抑涡格栅对宽幅分离式双箱梁涡振性能的影响研究

摘要

To investigate the suppression effects of the grid plates on the vortex-induced vibra-tion(VIV)of the separated wide twin box girders and the influences of the design parameters of the plates on the suppression effects,a long span suspension bridge with the separated twin stiffe-ning box girders was taken as an example and the sectional model wind tunnel tests for the plates of the bridge were carried out.The influences of the wind permeability ratios,bar width,layout ways and installation positions of the plates on the VIV performance of the girders of the bridge were studied,the characteristics of the sectional flow fields were analyzed,using the computation-al fluid dynamics(CFD)method and the causes leading to the VIV on the girders and the VIV sup-pression mechanism of the plates were revealed.The results show that the installation of the grid plates can effectively suppress the VIV of the separated wide twin box girders.The VIV amplitude of the girders increases first and decreases then with the increase of the wind permeability ratios of the plates and the 33% ~67% is deemed to be the optimal range of the permeability ratios.T he VIV suppression effects of the plates increase with the increase of the bar width of the plates.The VIV suppression effects of the uniform installation of the plates are better than those of the non-uniform installation of the plates.The suppression effects of the installation of the plates on the upper surface of the central opening of the separated twin box girders are more opti-mal than those of the installation of the plates on the lower surface.The aerodynamic force causing the VIV originates from the lift force of the simple harmonic variation at the downstream box gird-er.After the plates are installed,the wake vortex occurring at the upstream box girder is broken down by the plates and therefore,the lift force of the harmonic variation at the downstream box girder w ill be eliminated.%为研究抑涡格栅对分离式双箱梁涡振性能的抑制效果及格栅设计参数对其抑振效果的影响,以某大跨分离式双箱梁悬索桥为背景进行节段模型风洞试验,研究格栅透风率、格栅条宽度、格栅布置方式及设置位置对加劲梁涡振性能的影响,并采用计算流体力学(CFD)方法分析断面流场特性,揭示加劲梁产生涡振的原因及格栅的抑振机理.结果表明:设置格栅能有效抑制分离式双箱梁的涡振;分离式双箱梁的涡振振幅随格栅透风率的增加先增大后减小,33% ~67% 为最优透风率区间;格栅的抑振效果随格栅条宽度的增大而增强;格栅均匀布置比非均匀布置时抑振效果更好;在分离式双箱梁中央开槽上表面设置格栅比在下表面设置格栅抑振效果更优;产生涡振的气动力来源于下游侧箱梁处简谐变化的升力,设置格栅后上游侧箱梁产生的尾流旋涡会被格栅打碎,从而消除下游侧简谐变化的升力.