Study On The Influence Of Turbulence Integral Scale Based On The Wind Tunnel Pressure Test Of CAARC Model

The accuracy of the simulation of the wind characteristics in the wind tunnel test,determines the accuracy and even the rationality of the test results.Atmospheric boundary layer wind characteristics of the simulation are mainly wind speed,turbulence intensity,turbulence integral scale,and the turbulence integral scale is the most difficult part to simulate.Considering its poor simulation accuracy,wind tunnel laboratories do not generally use it as a primary consideration when using passive simulation techniques.This leads to a small scale of the turbulence integral of the simulated wind field when the wind tunnel test scale is large,and ultimately affecting the experimental results.Coupled with the rise of high-rise buildings,large-span structure,turbulence integral scale plays an increasingly important role,so it is necessary to carry out in-depth study.In order to realize the accurate simulation of turbulence integral scale,this paper is based on the direction of passive simulation technology.Firstly,the passive simulation strategy of each flow field is studied and a large number of wind tunnel tests are carried out.Through the study,the relationship between the passive simulation strategy and the turbulence integral scale is established,and then the four criteria of turbulence integral scale optimization are proposed.By optimizing the arrangement scheme of the passive simulation device,the turbulence integral scale of the simulation is improved by 50%,which effectively improves the limitation of the current passive simulation technology.Based on the wind tunnel test,the influence of turbulence integral scale on the results of pressure measurement is compared and analyzed.Firstly,with the help of the turbulence integral scale optimization criterion,this paper simulates two kinds of wind fields,which the turbulence integral scale are different,and the other parameters basically the same.Then the CAARC rigid model is tested by these two kinds of wind fields,and the results show that the turbulence integral scale has a great influence on the negative pressure test of the building: The average wind pressure coefficient is underestimated about 25%,the fluctuating wind pressure coefficient is underestimated about 20%,and the shape coefficient can be underestimated about 10%~20%.Based on the results of this paper,it is suggested that the negative pressure test results(wind pressure coefficient,shape coefficient)should be multiplied by a correction factor of 1.1 to 1.2.The influence of integral scale on the wind-induced response of high-rise buildings was studied by frequency-domain and time-domain analysis.Firstly,the CAARC model is analyzed by frequency domain using the fluctuating wind power spectrum obtained by wind tunnel test.The results show that the small turbulence integral scale leads to the underestimation of pulsation increase factor,thus underestimating the flow of wind and building resonance response.And the small rate is 10% according to this paper,while the result of time-domain is 15%.The study of time-domain also shows that the maximum displacement of the top of the structure is underestimated about 10%,the small rate of the maximum acceleration is even underestimated about 23%.Meanwhile,the structure response time course of small turbulence integral scale is less volatility,which is unfavorable to structural wind resistance design.Based on this paper,the structure response should be amplified about 1.1~1.2.