Numerical Investigation Of Aerodynamic Shape Effects On Vortex-Induced Vibration Of Bridge Girde

Modern bridge structures continue to develop in the direction of length,slenderness,lightness,and flexibility,while the stiffness and damping of the structure are correspondingly reduced,making it more sensitive to wind load response.When natural wind flows across the bridge section,flow separation and regular Vortex shedding will occur,and vortex-induced vibration of the structure will be excited in a certain wind speed range.Bridge vortex-induced vibration is a limited amplitude forced vibration with self-excited properties.Although it does not directly cause damage to the bridge structure,continuous vibration affects the comfort and safety of driving,and may also lead to fatigue failure of bridge components.Therefore,it has attracted widespread attention from people.Compared to traditional experimental research,CFD technology can not only visualize the flow field,but also save time and cost,and improve computational efficiency.In this thesis,focusing on the change of the geometric shape of the bridge section,with the help of the latest technology of computational fluid dynamics(CFD),the vortex-induced vibration characteristics of the bridge and the suppression measures of vortex-induced vibration are studied.The main research contents are as follows:Firstly,a systematic review of the research progress on vortex-induced vibration of bridge structures is conducted,and a brief introduction is given to the theoretical model of numerical simulation,Runge-Kutta method for solving vibration differential equations,and the entire process of implementing vortex-induced vibration of bridge structure sections using CFD dynamic grid technology combined with self-designed user-defined function(UDF)programs.Then,taking a rectangular cross-section with a aspect ratio of 4 as the research object,the feasibility of the UDF+Fluent dynamic grid method used in this paper is verified by comparing it with existing literature;Taking a rectangular section with a width to height ratio of 5 as the research object,the internal relationship between the three-divisional force coefficients of the bridge section and the variation of vortex shedding frequency with inlet wind speed were numerically analyzed;It was found that when the vertical bending fundamental frequency and torsional fundamental frequency of the structure are far apart,it is difficult for the structure to undergo bending torsional coupling vortex vibration;Captured phenomena such as "beat","phase jump",and "lock-in";Further understand the entire process of vortex-induced vibration by analyzing its flow field characteristics.Finally,by changing the aerodynamic shape of the rectangular section of the bridge,the influence of the shape of the rounded and chamfered corners on the vortex-induced vibration of the rectangular section is explored.This includes numerical simulation of vortex-induced vibration of rectangular sections with different sizes of rounded corner shapes and different tangential corner shapes,analysis of their vortex amplitude value,vortex shedding frequency,and phase difference between force and displacement.Through their flow field characteristics,the mechanism of the influence of corner shape on structural vortex vibration is understood,and relatively optimal vibration suppression measures are determined.