Aeodynamic Performance Optimization Of Bridge Section Based On Surrogate Model

This paper mainly studies the method of aerodynamic performance optimization of bridge section based on numerical simulation and mathematical strategy.Numerical simulation calculation refers to the use of computational fluid dynamics(CFD)numerical simulation and free coupling vibration method for calculation.The mathematical strategy is to combine experimental design,multi-objective particle swarm optimization(MOPSO)with proxy model,and use the method of uniform sampling in space to solve part of the solution of a bridge model section in the complete design domain,so as to construct an approximate proxy model that meets the accuracy requirements,and then all the solutions in the design domain can be obtained,so that the multi-objective particle swarm optimization(MOPSO)can be used.Taking the flutter performance of the bridge model section as the optimization objective and the main girder section of a bridge as the basic section for deformation,the aerodynamic performance of the optimized bridge section shows better wind resistance and wind vibration suppression effect,which has a significant effect on improving the stability and safety of the bridge structure.This study provides a new idea and method for the optimization of flutter performance of bridge section,and provides a certain theoretical and practical basis for the design and construction of bridge engineering.Future research can further explore the related problems of flutter performance optimization of bridge section.Aiming at the subject of flutter performance optimization of bridge section based on proxy model,this paper mainly carries out the following aspects:(1)CFD realization of free coupling vibration method.Firstly,the fourth-order RungeKutta method is discussed in detail.Secondly,the thin plate is used to replace the ideal plate,and the CFD calculation model is meshed,and the operation steps are briefly described.The critical flutter wind speed is quickly determined by using the two-dimensional flutter time domain method,and the results are compared with the experimental results.The results are in good agreement,which proves the accuracy of the calculation method in this paper,verifies the feasibility of UDF program and realizes the rapid determination of the critical flutter wind speed of the model section.(2)Study on the selection method of key parameters in optimal design.Firstly,the factors that affect the aerodynamic performance of bridge section are briefly described,and three of them(namely,nozzle angle,downward inclined web angle and nozzle position)are selected as the research objects of this paper.By using the improved Latin hypercube sampling method,a large number of CFD numerical simulations are carried out on the sampling results to complete the construction of the sample database.Among the above three factors,the most significant one is the flutter performance of the bridge model section.Using the regression analysis software of IBM Spss,the three independent variables(nozzle angle,downward inclined web angle and nozzle position)in the database and the dependent variables are the flutter critical wind speed corresponding to each bridge model section.By putting forward the hypothesis to verify the hypothesis and the analysis results,the most significant factors affecting the flutter critical wind speed of the bridge model section are finally obtained.(3)Select the most significant factors that affect the flutter performance of the bridge model section.By using regression analysis,the three independent variables(nozzle angle,downward inclined web angle and nozzle position)in the database and the dependent variables are the flutter critical wind speed corresponding to each bridge model section.By putting forward the hypothesis to verify the hypothesis and the analysis results,the most significant factors affecting the flutter critical wind speed of the bridge model section are finally obtained.(4)Predictive analysis based on agent model.Based on the software of Isight parameter optimization analysis,four proxy models,namely orthogonal polynomial,Kriging,radial basis function and response surface,are constructed,in which the independent variable is the dip angle of the downward inclined web,and the dependent variable is the critical flutter wind speed of the bridge model section.Thirteen sample points are randomly selected for CFD calculation,and compared with the predicted values,the error between the numerical simulation and the predicted results is calculated.The results show that the Kriging proxy model has the highest accuracy.results are compared and verified,which shows the feasibility of the optimization design method.(5)Optimal design based on multi-objective particle swarm optimization.An optimal design method for predicting aerodynamic shape based on surface pressure gradient of bridge model section is proposed.The characteristic area of surface pressure gradient is extracted from the bridge model section.Based on the platform of Isight parameter optimization analysis,a Kriging proxy model with the characteristic area of surface pressure gradient as the dependent variable is established,and then it is optimized by using multi-objective particle swarm optimization algorithm in the two established Kriging proxy models respectively,and the optimized results are 16.226 and 15 bridge sections,which improves the bridge.The optimized model section is calculated by numerical simulation,and the results are compared and verified,which shows the feasibility of the optimization design method.