Study On The Influence Of Wind-fence Under Crosswinds On Traffic Safety Of Expressway Tunnels Exit

The social and economic development of the Beijing-Tianjin-Hebei region has placed higher demands on the quality and service level of expressway networks.The relevant construction departments have continuously built and reconstructed expressways in the congested sections where traffic volume is concentrated.In recent years,the mileage of newly construction and rebuilt highways has reached more than 30,000 kilometers.At the same time,in the highway construction project in the hilly area of the mountainous area,more and more construction departments use the engineering means of excavation tunnels to smooth the expressway line shape.Exit of the tunnel is prone to traffic accidents caused of strong air currents.In the North China region,windy weather often occurs.The airflow flows through the tunnel exit of the mountainous highway,the wind speed in the inside and outsiden the tunnel mouth changes drastically.The driver cannot predict the crosswind force in advance.When the vehicle speed is high,the lateral airflow has a great influence the vehicle balance.The aerodynamic forces generated by the crosswind will cause the vehicle to slip or even roll over.Therefore,it is important to study the impact of the tunnel side wind disaster on traffic safety.At present,relevant researches at home and abroad are in the stage of continuous development and innovation.This paper attempts to study the wind characteristics of the wind-fence under the crosswind at the tunnel exit and analyze the impact of the wind-fence on the driving safety.In this paper,the cross section of the common one-way two-lane tunnel is taken as the research object.The large-scale commercial software ANSYS is used for numerical simulation.The meshing tool is used for strict mesh division.The numerical solution is based on two-dimensional viscous incompressible N-S equation and SST k-omega turbulence model establishes a numerical calculation model for the airflow field near the tunnel exit of the mountainous highway under the crosswind effect of the Deflection angle of 90(the angle between the crosswind direction and the direction of the vehicle).The influence of the porosity of the wind-fence on the crosswind is analyzed,and the applicability of the wind-fence under different intensity crosswind conditions.The transient simulation technique is used to analyze the variation of the flow field of the model under the crosswind environment with time.At different time points the influences of two kinds of wind-fence models,no wind-fence model,one-car passing and two-car passing on the aerodynamic coefficient lateral force S and lift L of van,and analysis Its role in driving safety.The simulation shows that the wind-fence velocity distribution is related to the porosity after the wind-fence is set under the crosswind.The wind-fence porosity is between 20-30%,which can effectively weaken the crosswind,improve the safety of driving.The 25% porosity wind-fence has strong applicability.The flow field generated by the crosswind disaster changes with time.The wind-fence with 25% open porosity can reduce the lateral force by about 21% for the non-opened wind-fence.There is no significant effect on the lateral force of the wind-fence through one car or two cars.The work of this paper has certain reference to the aerodynamic problems of car which through the tunnel exit of the expressway,safety problems and the problem of setting the wind-fence,and has certain reference value for the safe operation of the expressway tunnel.