Study On The Influence Mechanism Of The Coupling Effects Of Wind And Rain On The Aerodynamic Performances Of High-speed Railway Bridge And Vehicle

In recent years,China’s high-speed railway construction has developed rapidly.Its operating mileage continues to grow.But the meteorological disasters that high-speed railway suffered are becoming more and more complex.Windstorm and rainstorm are the two most common meteorological disasters.In the gale and rainstorm,the aerodynamic performances of high-speed railway bridge and vehicle will be changed.Then the running safety of high-speed railway will be affected.In this study,the joint probability distribution model based on the mixed Copula function is presented to describe the joint distribution law of daily extreme wind velocity and rainfall intensity monitored by 5376 base station along Lanzhou-Xinjiang high-speed railway.The three dimensional static component forces of bridge and vehicle under the coupling effects of wind and rain are analyzed on the basis of basic rainfall characteristic parameters.Then the aerodynamic model of high-speed railway bridge and vehicle under the coupling effects of wind and rain is eatablished by using computational fluid dynamics software FLUENT.And the influence mechanism and change law of wind speed,rainfall intensity and wind attack angle on the aerodynamic performances of high-speed railway bridge and vehicle are further studied.The main research contents and conclusions are as follows:(1)Based on the analysis of impact of the coupling effects of wind and rain on the operation safety of high-speed railway bridge and vehicle,the main use of a large number of original wind velocity and rainfall intensity accumulated in the high-speed railway disaster prevention network is explained.A review is performed for the joint probability distribution model of wind velocity and rainfall intensity,the coupling effects of wind and rain,and its impact on the aerodynamic performances of bridge and vehicle.Drawbacks in existing studies are pointed out,and the significances of establishing the joint probability distribution model of wind velocity and rainfall intensity based on real disaster and studying the impact of the coupling effects of wind and rain on the aerodynamic performances of high-speed railway bridge and vehicle is elaborated.(2)Based on the analysis of two elliptic Copula functions and three Archimedean Copula functions,the mixed Copula function is constructed.Then the joint probability distribution model of wind velocity and rainfall intensity based on the mixed Copula function is established by nonparametric kernel density estimation,the Bayesian weighted average method and the rule of minimum of sum square variation.And the model is verified to be the best model to describe the joint distribution law of daily extreme wind velocity and rainfall intensity monitored by 5376 base station along Lanzhou-Xinjiang high-speed railway by using the K-S test and the minimum distance test.(3)Based on the analysis of basic rainfall characteristic parameters,the Best raindrop spectrum model is selected to describe rainfall events,and Fabien J.R van Mook formula is used to calculate the terminal velocity of raindrop.Then the change of wind pressure and wind-driven rain intensity under the coupling effects of wind and rain are discussed by calculation formulas of wind pressure and wind-driven rain intensity.Finally,the impact force equation of a single raindrop on the structure is established on the basis of corresponding basic hypothesis and momentum theorem,and the formulas for calculating the three dimensional static component forces of bridge and vehicle under the coupling effects of wind and rain are derived according to the static wind load calculation formula of bridge and vehicle.(4)Based on the basic theory of fluid mechanics,the aerodynamic model of high-speed railway bridge and vehicle under the coupling effects of wind and rain is eatablished by using computational fluid dynamics software FLUENT.The above modeling method is validated using the wind tunnel tests conducted by Dr.Lei Xu of Hunan University.And the drag coefficient increments of bridge deck section under different rainfall intensity are in good agreement.It fully verifies the accuracy and reliability of the above modeling method.(5)Based on the verified joint probability distribution model of wind velocity and rainfall intensity and established aerodynamic model of high-speed railway bridge and vehicle under the coupling effects of wind and rain,the wind velocity and rainfall intensity that meet one hundred years return period are selected to study the effects of key properties on aerodynamic performances of high-speed railway bridge and vehicle under the coupling effects of wind and rain.The key properties include wind velocity,rainfall and wind attack angle.The results show that the influence of different parameters on aerodynamic performances of high-speed railway bridge and vehicle under the coupling effects of wind and rain is different.The wind velocity has a great effect on aerodynamic performances.With the increase of wind velocity,the three dimensional static component forces increase,and the lift coefficient and moment coefficient also increase,but the drag coefficient decreases.The rainfall intensity has little effect on aerodynamic performances.With the increase of rainfall intensity,both of the three dimensional static component forces and their coefficients increase slowly.Finally,with the increase of wind attack angle,the drag coefficient of bridge increases,but the drag coefficient of vehicle decreases,and their lift coefficient and moment coefficient both decrease.