Research On Vortex-induced Vibration Of Long-span Suspension Bridge And Its Aerodynamic Measures Based On FLUENT

With the continuous development and progress of modern bridge construction technology,more and more long-span bridges begin to be built.Because of its characteristics of soft,weak damping,low natural frequency and close to the action frequency of strong wind,the wind-induced dynamic response has become an important factor in the design of long-span bridges.Vortex-induced vibration(VIV)is one of the forced and self-excited wind-induced vibration.Because of its low starting wind speed,it is easy to occur in bridge structures,and has gradually become the focus of bridge wind resistance research.At present,wind tunnel test is still the main method to study this kind of problem,but it also has its limitations.The flow field can not be visualized and the vortex vibration mechanism can not be analyzed;The development of computational fluid dynamics(CFD)provides another research method for vortex-induced vibration problems.By using CFD method to emulate and simulate according to the actual wind environment,a lot of complicated work can be avoided and the cost can be reduced.At the same time,the flow field visualization can be realized and the aerodynamic characteristics can be predicted intuitively.In this paper,Fluent software is used as a calculation tool,a better quality mesh model is divided in Pointwise software,and a UDF program for solving the two-dimensional single degree of freedom vertical bending vortex-induced vibration problem based on the fourth-order Runge-Kutta method is compiled.The following research contents are carried out:Firstly,based on the Fluent dynamic grid technology,The two-dimensional static flow and dynamic flow around a rectangular section with aspect ratio of 4:1 are simulated.The numerical simulation results in this paper are in good agreement with the experimental results and other numerical solutions,which verify the feasibility of grid generation and the accuracy of self-edited vortex-induced vibration calculation program UDF.Then,the static and dynamic flow around the design section of a long-span suspension bridge under construction and completed conditions are simulated.The aerodynamic characteristics of the design section are obtained through the analysis of its aerodynamic parameters.With the help of post-processing software,the whole process of vortex vibration is understood from the mechanism,which provides the basis for the next optimization of aerodynamic measures.Finally,according to the mechanism of the vortex-induced vibration of the designed cross-section in the bridge completed state,two aerodynamic optimization measures are proposed,namely the handrail flow suppression plate and the movable handrail base,but the vibration suppression effect is not ideal.Then,the movable handrail base and the splitter plate are used as the combination of aerodynamic measures,and the significant vibration suppression effect is achieved.