Experimental Study On Aerodynamic Characteristics Of Three Square Cylinders Arranged In Line

Square cylinders are widely used in civil engineering structures,such as piers,towers,offshore drilling platforms,high-rise buildings,etc.Different from the flow around a single square cylinder,the flow around square cylinder is more peculiar when a group is formed,resulting in complex aerodynamic interference between the cylinders.At present,most researches on the three square cylinders arranged in line are in tandem or side by side,but there are few researches on the other wind direction angles.For three square cylinders,wind direction angle is one of the important factors causing aerodynamic interference,and square cylinders with different wind direction angles and spacing ratios will produce different aerodynamic interference to each other.In this paper,a rigid model wind tunnel test was used to test and study the interferences effect of aerodynamic characteristics of three square cylinders arranged in line,where the wind direction angles were 0°～90° and the spacing ratios L/D=1.2～8.0.The main work of this paper is as follows:(1)A new device was developed for testing the aerodynamic characteristics of the three square cylinders arranged in line,which can adjust the spacing ratios conveniently and the wind direction angles,greatly improving the test efficiency.(2)Compared with the test results of the single square cylinder,the interference of the average and pulsating wind pressure coefficients distribution of the three square cylinder was obtained.The results show that the wind pressure distribution is mainly affected by reducing effect.the distribution of wind pressure is completely different before and after the critical spacing ratios.(3)Compared with the test results of the single square cylinder,the interference of the average and pulsating aerodynamic coefficients of the three cylinders arranged in line was obtained,the results show that the critical spacing of aerodynamic coefficients of the three cylinders arranged in line was observed at small wind direction angles(α=0°～10°)and large wind direction angles(α=80°～90°).In the critical spacing ratios,the aerodynamic coefficient will occur "jump";In the range of medium wind direction angles(α=15°～75°),The aerodynamic coefficient has obvious consistency with the change of the spacing ratios.(4)Compared with the test results of the single square cylinder,the interference of the vortex shedding characteristics of the three cylinders arranged in line was obtained,the results show that the critical distance is more complicated than that of the three square cylinder vortex under the small wind direction angles and the large wind direction angles.In the critical spacing ratios,the aerodynamic coefficients of the square cylinders have abrupt changes.The Strouhal number of the three square cylinders outside the critical spacing ratios gradually approximated the test results of the single square cylinder.In the range of medium wind direction angles,the variation law of Strouhal number with spacing ratios is basically the same.