本文係以風洞實驗方法探討矩形柱在均勻 紊流場中所受橫風向風力作用之各項特性。實 驗以矩形柱之長寬比,及紊流強度及長度尺度為 參數,量測矩形柱所受之側面風壓 C/sub p/,橫風向 昇力係數C/sub 1/,史特赫數St和橫風向風力頻譜等 ,實驗結果顯示代表幾何形狀的長寬比為影響矩 形柱風向風力的最主要參數。當長寬比接近0.6 時昇力係數會達到一極大值。長寬比愈大則渦 散現象將因分離剪力層流的再附著現象而產生 渦散頻率降低及渦散強度減弱的現象。 The fluctuating wind loads acting on high rise structures in atmospheric boundary layer is a complex aerodynamic phenomenon. There exists no credible analytical model which can predict wind loads accurately. This research project studied the acrosswind forces on rectangular cylinders in smooth and homogeneous turbulent flows through wind tunnel studies. Depth-width ratio of cylinders and turbulence features were chosen to be the controlled parameters. Pressure coefficient, lift coefficient, Strouhal number and power spectral density of acrosswind forces were measured. The results indicate that the depth-width ratio is the dominant factor in terms of vortex shedding process and the corresponding acrosswind forces. The lift force reaches maximum when depth-width ratio is about 0 .6. For large depth-width ratio the vortex shedding process will be damped significantly due to surface reattachment mechanism.
關聯:
中華民國力學學會第十五屆全國力學會議論文集(一)=Proceedings of the 15th National Conference on Theoretical and Applied Mechanics (I)，頁137-144
