Investigation Into Influencing Factors On Wind Tunnel Test Of Vortex-induced Vibration And Mechanism

The development direction of modern bridge is long span, thin, light, soft and lowdamping, then more sensitive to the wind effect, the problem of aero elasticity has been therestraining factor on strength, stiffness and wind resisting stability of large span bridges andsuper large span bridges. Vortex-induced vibration of bridge is a kind of wind inducedvibration and is vibration amplitude limit with properties of forced and self-excited.Vortex--induced vibration although will don’t cause the catastrophic destruction of bridge asthe flutter, but it happened frequently on low wind speed and leading to stem crack or fatiguedamage will influence security. So the vortex-induced vibration is a very important problemof bridge wind engineering field. Considering the research of vortex-induced vibration ismore important and more, this paper systematically proceed to the research of vortex-inducedvibration angle-attack effect, Reynolds-number effect, size effect and wind field effect ofstreamline-like section and section with projecting slab and reveals the inner mechanisms. Inthe end, the paper put forward proposal for wind test method of vortex-induced vibration.This text main focuses on following research:1. Vortex-induced responses of streamline-like section on different angle-attack wereinvestigated. Pressure taps were set on the model surface, pressure time history of all the tapswere measured by pressure scanning when vortex–induced vibration occur on differentangle-attack. The rules of vortex-induced response and surface pressure distribution withangle-attack were investigated. The results show that the change of angle-attack is essentiallychanged aerodynamic appearance. St Number is not same on different wind angle-attack.2. By changing model dimension to change Reynolds-number, the vortex-inducedresponse’s Reynolds-number effects of streamline-like section and section with projectingslab were researched. The paper reveals Reynolds number influence on vibration spectrum, onfluctuating pressure power spectrum, on surface pressure distribution, and fluctuating pressurecoefficient. The results show that the internal cause of vortex-induced resonance Reynoldsnumber effect is the Reynolds number effect on correlation of points and total aerodynamicforce and fluctuating pressure coefficient. 3. The size effect of vortex-induced responses was investigated by wind tunnel tests. Bychanging the model width to change length-width ratio, and pressure taps were set on themodel surface at the half, quarter and eighth, the vortex-induced force differences of differentsetting were researched. The results show that the length-width ratio of model forvortex-induced response should be near1.5.4. By grille to form turbulent flow, the vortex-induced response differences of uniformflow and turbulent flow were researched. The results show that the vortex-induced responsewill be reduced even disappeared. The internal cause is the airflow correlation has beendestroyed by fluctuating composition in the turbulent flow. The abilities of transforming andretroaction to turbulence have been reduced, the form of vortex bas been blocked, sovortex-induced response will be reduced even disappeared in the turbulent flow.