圆柱结构涡激共振耦合效应及其抗风设计参数

Coupling Effect of Vortex Induced Vibration on Circular Cylinder and Its Parameters on Wind Resistance Design

为了解决亚临界区圆形断面细长结构涡激共振抗风设计参数取值不明确的问题,针对土木工程领域小直径圆形细长结构在亚临界区的涡激共振现象,对其涡激共振耦合效应进行了研究,获得其抗风设计的主要气动力参数。采用弹性悬挂节断模型风洞试验,模型两侧采用斜置上下不等刚度的弹簧提供三自由度的振动模型,试验风速对应的雷诺数区位于亚临界雷诺数区,分别测试风速增大和减小2种状态下模型的涡激共振,试验采用激光位移计和压力扫描阀同步测试模型振动位移和表面风压,通过分析位移和风压之间的关系,揭示涡激共振发生的耦合状态,并基于涡激共振抗风设计的要求,给出涡激共振锁定区间、气动力系数等抗风设计参数。结果表明:风速增大和减小2种状态下,涡激共振的耦合状态不同,风速增大过程中锁定区间更长;在锁定区间内存在强耦合和弱耦合2种机理的耦合状态,强耦合状态下的升力系数标准差和平均阻力系数值更大,旋涡脱落频率更强,气动力和流场的波动也更强;基于此,建议在对亚临界区的圆形断面结构进行涡激共振设计时,锁定区间为1.0~1.3倍起振风速,其中1.0~1.1倍起振风速范围内按照强耦合状态设计并考虑由耦合效应引起的气动力增强,1.1~1.3倍起振风速范围内按照弱耦合状态设计。

This research focuses on vortex induced vibration（VIV）in the sub-critical Reynolds number range of a circular cylinder with a small diameter for application in civil engineering.In this study,the coupling effect in VIV is investigated to determine the parameters for its wind resistance design.The research mostly involved wind tunnel tests of elastically mounted section models.Four springs with different stiffnesses at the upper and lower ends are inclined at each end to provide a vibrating model with three degrees of freedom.The VIV is measured during increasing and decreasing wind velocity corresponding to the sub-critical Reynolds number range.The displacement of the model and wind pressure distribution on the model are synchronously measured using laser meters and pressure scanners,respectively.The coupling state of VIV is determine by analyzing the relationship between the displacement and pressure distribution.Based on the requirement for wind resistance design,parameters such as the wind velocity range of‘lock-in＇and the aerodynamic force coefficients are investigated.The results show that the coupling states are different for increasing and decreasing wind velocity;the wind velocity range of‘lock-in＇is larger in the increasing wind velocity state than in the decreasing state.When‘lock-in＇occurs,there are strong and weak coupling states.The standard deviation of the lift coefficients and the mean drag coefficients are larger,the vortex shedding is stronger,and the aerodynamic force fluctuation and flow state are also stronger in the strong coupling state than in the weak coupling state.These results indicate that when the circular cylinder-like structure is designed according to the resistance in VIV,the‘lock-in＇range of 1.0-1.3 times that of the onset wind velocity of VIV is proposed.The enhancement of aerodynamic forces induced by the strong coupling effects should be considered when the wind velocity is 1.0-1.1 times that of the onset wind velocity of VIV.When the wind velocity is 1.1-1.3 times that of the onset wind velocity of VIV,the aerodynamic forces are determined with respect to the weak coupling state.