Numerical Simulation Of Flutter Derivative Of Typical Girder Section

Bridge flutter poses a great threat to people’s life and regional economic development,so it should be avoided in the design of bridge wind resistance.In this paper,CFD modeling tool,FLUENT as a solution,MATLAB as a data processing tool,thin plate section,streamlined section and shape blunt body section as the research objects.The main research work includes flutter derivative identification,flutter stability analysis and nonlinear component analysis.The main contents and conclusions of this paper are as follows:（1）Taking thin plate section,streamlined section and shape blunt body section as the research object,the numerical simulation results of the three-component force coefficient of the main beam section were calculated,and the numerical results were compared with theoretical solutions or experimental results to verify the reliability of the numerical method.（2）Two sets of different hybrid grid computing models and one set of global unstructured grid computing models were set with thin plate section at 0°wind Angle of attack as the research object.The advantages and disadvantages of the three sets of schemes were analyzed from the three aspects of modeling difficulty,computing accuracy and computing time.（3）Eight flutter derivatives of the thin plate at 3°,5°and 7°of wind attack angle were identified by sub-state forced vibration.The results showed that,under the action of different wind attack angles,except for A₄^*,the numerical results of the curve of variation of the flutter derivatives with wind speed reduction were consistent with the overall trend of the experimental results.Except that the simulation errors of H₂^*and A₄^*at 5°and H₄^*and A₄^*at 7°were large,the numerical results of flutter derivatives were better.Wind speed decreases with the increase of the wind angle of attack（H₂^*,A₄^*and H₄^*are flutter derivatives,indicating the influence of aerodynamic self-excited force on lift force and moment of structure）.（4）The variation of flutter derivative and flutter critical wind speed of sutong bridge under the conditions of different wind angle of attack,different nozzle height,different angle of inclined web and different length of flow guide plate is explored,which provides the basis for the section design of the main beam of long-span bridge with the aspect ratio of 10.（5）The flutter derivatives of type blunt body are identified and the high order harmonic components in the aerodynamic data are analyzed.The results showed that the first-order and second-order components accounted for more than 85%of the total self-excitation force,while the third-order and higher-order components accounted for less.