1.College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China;
2.Electric Power Design Institute of Zhejiang Province, Hangzhou 310007, China
In order to study the aerodynamic coefficients and flow characteristics of a smooth circular cylinder, wind pressures on the cylinder were measured at different wind speeds in a uniform flow simulated in a wind tunnel.The variation of the drag coefficient, lift coefficient, surface wind pressure distribution, wind pressure correlation coefficient and Strouhal number of the cylinder with respect to the Reynolds number were obtained.And the above results were compared with those of the previous researches.The results show that the fluctuation of the lift coefficients is larger than that of the drag coefficients, indicating that the vortex shedding induced by cross-wind excitation is more significant than that induced by along-wind turbulence.When the Reynolds number is in the critical flow region, the wind distribution around the cylinder experiences a symmetry-asymmetry-symmetry transition, revealing a whole changing process from laminar flow separation to turbulent flow separation.When the Reynolds number equals 352 000, a critical flow with laminar flow separation on one side and turbulent flow separation on the other side occurs and the wind pressures around the cylinder present a unilaterally asymmetrical bubble form.The characteristics of wind pressure correlation during laminar flow separation and turbulent flow separation were obtained.The wind pressures on the same side of the cylinder are highly correlated in the laminar flow separation case.Whereas, the wind pressures in the flow region before the separation point are highly correlated and those in the flow region after the separation point are weakly correlated in the turbulent flow separation case.The spectrum of lift coefficient has an obvious peak in the turbulent flow separation case, indicating that the fluctuation of the wind pressures is induced by the periodical vortex.The spectrum of lift coefficient has no obvious peak in the turbulent flow separation case, indicating that the fluctuation of the wind pressures is induced by the random vortex.
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