|Abstract: ||本文以風洞模型實驗方法探討發生橫風向振動時,矩斷面柱體所受風力特性的改變。模型試驗中以振動頻率及振幅為控制條件,量測從事簡諧運動模型的表面風壓。經由風壓組合後可得各種風壓係數,整體風力頻譜,並求得與振動速度同相位的氣動力阻尼。實驗結果顯示,小於臨界深寬比的矩柱,振動時會增強渦散,引發流場共振,提高橫風向風力。長寬比大於 1.0的矩柱上述現象並不明顯。矩柱具有明顯的氣動力效應,忽視結構-流場互制現象可能會嚴重影響結構受風反應。|
The aerodynamic characteristics of oscillating rectangular cylinders in turbulent boundary layer flows were studied through wind tunnel model tests. Experimental parameters such as: depth-to-width ratio, flow features, vibration amplitude and vibration frequency were used to study the motion effects on aerodynamic damping, mean and r.m.s. force coefficients, power spectral densities, spatial correlations and local pressure of the rectangular cylinders. The results indicate that, for model with depth- to-width ratio smaller than critical value, acrosswind oscillation will amplify the so call "synchronization" phenomenon, increases the mean and r.m.s. force coefficients. Aerodynamic damping coefficients coupled with force spectra obtained through stationary pressure model tests were used to estimate the acrosswind response. The results show that, for cylinders with depth-to-width ratio smaller than critical value, neglecting motion induced force will underestimate the structural response significantly.