Study On Average Wind Characteristics And Upstream And Downstream Wind Field Distribution Of Bridge Site In Complex Mountainous Areas

In recent years,the construction of long-span bridges in mountainous areas is increasing.It is a difficult problem to determine the reference wind speed of bridges in mountainous areas.The existing Wind-resistant Design Specification for Highway Bridges is based on the historical wind speed data in the eastern plain area,which has limited reference significance for bridges in mountainous areas,so it is necessary to study the wind characteristics in mountainous areas.In this thesis,the computational fluid dynamics software FLUENT is used to study the wind characteristics of ideal V-shaped and U-type gorges,and the width and height of different sections of two kinds of ideal gorges are discussed,and the influence of various parameters on the wind characteristics of gorges is analyzed.Meanwhile,two kinds of ideal gorges sections and ideal river course are combined.The ideal river course include straight river course,Stype river course and Y-type river course.The wind characteristics of different river course are studied.At the same time,taking the Daduhe railway bridge site as the engineering background,this thesis studies the distribution of wind characteristics in the complex mountainous with CFD numerical simulation.Based on the numerical simulation,this thesis proposes a method to find the correlation of two-point average wind speed in the downhill river.The results show that in V-type and U-type canyons,the larger angle or width of gorge sections is,the weaker acceleration effect is.The higher the canyon is,the stronger the wind speed acceleration effect is.The amplification effect of wind speed has a linear correlation with the angle of V-type gorge and a logarithmic correlation with the width of U-type gorge.In the straight river course,the wind speed amplification factor at the entrance of gorge is relatively high,and the wind speed amplification factor gradually decreases along the river course,and finally becomes stable;In the S-type river course,the river course bending has a certain reduction effect on the wind speed,and it gradually increases with the increase of the river course bending degree.In addition,there may be a certain acceleration effect of wind speed after the bend of the river.The wind characteristics of Y-type is relatively complex.The wind characteristics in each river course varies greatly with different incoming wind directions.At the same time,there is also a large wind attack angle.Under a certain incoming wind direction,the wind direction at the bottom and upper part of the river course may be reversed.In the complex mountainous areas,the various outstanding mountains are important factors that cause the complex distribution of wind characteristics,which may cause wind speed reduction or increase,and may cause abnormal distribution of yaw angle and wind attack angle.It needs special consideration in wind field analysis.There is a certain correlation between the average wind speed of two points in the same river course under different incoming winds.The relationship between the average wind speed of two points can be obtained by fitting the average wind speed of two points under different incoming winds through numerical simulation.