Numerical Simulation Study Of Wind Flow Over Complex Terrain And Wind Load On An Angle Steel Transmission Tower

Numerical simulation is a powerful means to describe wind field details over mountain area,which can provide data for wind resistance analysis of building structures.Load code for the design of building structures has been specified for wind load in wind field over typical terrain.In view of the complexity of complex terrain,the wind field over complex terrain can't rely on the provisions of wind field over typical terrain.Therefore,in order to further strengthen the understanding of wind field over complex terrain and make up the shortage of load code for the design of building structures,it is necessary to carry out numerical simulation of wind flow over complex terrain.In this paper,a boundary condition of equilibrium atmospheric boundary layer is first obtained by numerical simulation,and the method of obtaining wind fields parameters over various terrains is determined.Then,a complex terrain model is established by digital elevation data.Based on RANS approach,the numerical simulation of wind flow over complex terrain is carried out by using FLUENT.The variation of wind speed ratio and wind direction considering the effect of complex terrain is studied,and the wind profiles of a site under different wind angles are also obtained.The results show that wind speed ratio and wind direction for one terrain are not affected by the change of inlet velocity profile,and the values in different terrains become different.The difference of wind speed ratio in different terrains is above 12%,and the difference of wind direction is larger,reaching to 40%.The overall modeling of transmission tower is established with the UG and GAMBIT software.Then,the shape coefficients of wind load on an angle steel transmission tower under different reference wind speeds and wind directions are obtained,and the standard values of wind load considering the effect of complex terrain are compared with code values.The results show that the reference wind speed has a little influence on the value of shape coefficients.The shape coefficients of wind load on portrait and landscape directions are both increase at first and then decrease with wind direction increasing for the tower body.The variation of shape coefficient on cross arm and tower body is nearly consistent.The simulated shape coefficients of the angle steel transmission tower are above 20% larger than the code values.Due to the acceleration effect of topography on wind speed and the less code values of shape coefficients under some wind angles,the standard values of wind load in wind flow over complex terrain are almost twice as much as code values.The results have reference value for the determination of wind load on angle steel transmission tower in wind flow over complex terrain.