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A study on the characteristics of surface pressures of rectangular cylinders in uniform turbulent flow and numerical verification
|關鍵字:||2D rectangular cylinders;二維矩柱;wind tunnel test;surface pressure;computational fluid dynamics;風洞實驗;表面風壓;計算流力||出版社:||土木工程學系||摘要:||
A series of aerodynamic experiments on 2D rectangular cylinders with variant depth-to-width ratio (D/B) were conducted to investigate the aerodynamic characteristics, included surface pressures coefficients, probability distribution type and independent peak events. The numerical computation procedures, with LES schemes, were also adopted to verify the results of aerodynamic experiments.
The results shown, the drag coefficients will be decreased as the depth-to-width ratio is increased, and the trends will be changed with small variant angle of approaching flow. The pressure coefficients of side face and rear face of cylinders with small depth-to-width ratio were affected by the turbulence intensity of approaching flow, but the affection will be inversed in the flow field with small angle of approaching flow.
The K-S test method was adopted to identify the distribution type of probability of wind pressures. The results have shown the PDF will close to normal-type and log-normal type for most cases but the pressure signals at side face and rear face with small depth-to-width ratio. The surface pressures of cylinders, depth-to-width equal to 1.0 and 4.0, were also measured with small angle of approaching flow. The result shown, the PDF of side face pressures will close to normal and log-normal type. The increasing of turbulent intensity will promote the type of PDF of surface pressures closer to normal and log-normal type.
The probability distribution of independent peak events at side face and rear face of cylinders will be more uniform as the turbulent intensity increased, but the values will be slightly decreased. With small angle of wind and the side face change slightly into the front face, the probability of independent peak events will be decreased but in the same time will be increased at the rear face. For the ensemble average of peak events, only the front face will be affected by the change of turbulent intensity. The PDF of independent peak events were found to be identical to the type I distribution type.
The numerical simulation results were quite similar to the result of aerodynamic experiments in the condition of small angle of approaching flow. For the cases of angle larger than 10 degree and high turbulence intensity, there were lots of differences between the simulated results and experiments results.
Keyword: 2D rectangular cylinders, wind tunnel test, surface pressures, computational fluid dynamics
|Appears in Collections:||土木工程學系所|
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