Inflow Turbulence Generation Technique For Large Eddy Simulation And Research On Surface Wind Pressure Of Five Arch Folded Space Truss Structures

The five arch folded space truss structure featuring rapid expansion of the space,light weight and repeated use is convenient for storage and transportation,which can be used in the field of military engineering and civil engineering.Its characteristics of folded space truss structures determine that it is sensitive to the wind load.It is also the control load of the structure design.At present,our specification does not propose the method on how to evaluate this kind of structure's wind load shape coefficient.Therefore,this paper researched on the surface wind load of five arch folded space truss structures by using large eddy simulation(LES)calculation,which is of great engineering practical value.Folded space truss structures are located in the atmospheric boundary layer,and that conditions of generation of turbulence inflow match the realistic wind flow characteristics in atmospheric boundary layer(ABL)is one of the premises of using LES to accurately predict the wind effect on structures.Previous research on numerical simulation of wind effects on structures is mostly used by RANS with stable entrance,or entrance of which the fluctuating wind characteristics are greatly different from those of ABL,contributing to unprecise result.Thus,a generation of turbulence inflow conditions for LES which can match the wind flow characteristics of ABL is obviously significantThis paper introduced the method and theory of structure wind resistance research,as well as large eddy simulation of computational fluid dynamics(CFD)numerical simulation as an essential method of the numerical wind tunnel simulation.Firstly,in view of the large eddy simulation numerical wind tunnel technology,the authoranalyzed the features of turbulent fluctuating wind and three widely used method for generating fluctuating wind,and depicted a new method to generate inflow turbulence:discretizing and synthesizing random flow generation(DSRFG).Secondly,based on Karman wind speed spectrum,the fluctuating wind speed time series generated by Matlab programming was elaborated,and it was successfully inserted in the entrance of CFX flow field analysis software.Then,the author used the method to calculate square cylinder and standard high-rise building structure model to verify the correctness of the method in this paper,proving that the method can better restore the atmospheric boundary layer wind characteristics.Finally,this paper carried out the simulation of five arch folded space truss structures numerical wind tunnel with the validation method for generating inflow fluctuating wind,and studied the characteristics of external flow field and surface wind pressure distribution.With the wind direction of 0 °,average wind pressure coefficient on the surface of five arch folded space truss structures is symmetric along the long axis of structure,of which most of surface bears negative pressure.The involved areas cover only about12.77% of the total area of the surface of the structure.Maximum wind load shape coefficient is 0.81,which is located in the lower part of windward area,while the minimum wind load shape coefficient is-0.73,which is located on both sides of the first frame in the main structure close to the windward face.With the wind direction of90 °,average wind pressure coefficient on the surface of five arch folded space truss structures is symmetric along the short axis of structure,of which most of surface bears negative pressure.The involved areas cover only about 24% of the total area of the surface of the structure.Maximum wind load shape coefficient is 0.81,which is located in the middle and upper part of windward area,while the minimum wind load shape coefficient is-0.88,which is located at the top of the main structure.With the wind direction of 90 ° and 0 °,the gap between shape coefficient given in standards and that calculated in this paper is 9% ~ 88%,and 8% ~ 70%.In the design of structure wind resistance,researchers should consider that the local wind pressure is greater than the average wind pressure,and avoid the emergence of various kinds of edges and corners.