本研究將探討一二維方柱體在受強制振動影響下,改變其橫風向與扭轉向振動間的頻率比及二維方柱之偏心量,進而瞭解橫風向與扭轉向振動間發生耦合時,結構物所產生之氣動力現象。 結果顯示,當Fr大於1.0時,在勁度中心往上游偏離,偏心量為10%時可得最小的擾動昇力係數峰值及渦散頻率的尾跡風速;而在勁度中心往上游偏離,偏心量為20%可得最大的擾動昇力係數峰值及渦散頻率的尾跡風速。當Fr等於1.0時,在勁度中心往上游偏離,偏心量為10%時可得最大的擾動昇力係數峰值及渦散頻率的尾跡風速;而在勁度中心往上游偏離,偏心量為20%可得最小的擾動昇力係數峰值及渦散頻率的尾跡風速。與Fr大於1.0正好相反。當Fr小於1.0時,在勁度中心無偏離時,可得最大的擾動昇力係數峰值及渦散頻率的尾跡風速;而最小值則不一定發生在哪一個偏心上。 Wind tunnel measurements were performed to study the aerodynamic phenomenon of a two dimensional prism when the mass center separates from the center in transverse and torsional coupled vibration modes.
When the torsion/transverse frequency ratio (Fr) is greater than 1.0, as long as the eccentricity is introduced in the upstream direction at 10%, the spectral peaks of the lift fluctuation coefficient and the vortex shedding reach a minimum value compared with other eccentricities. However, as the eccentricity increases to 20%, the spectral peaks reach a maximum value.
Whereas when Fr=1, eccentricity 10% and 20% in the upstream direction, the spectral peaks of lift fluctuation coefficient and vortex shedding show the opposite trend. A maximum value is obtained when Fr is smaller than 1.0 and without eccentricity. However, there is no obvious trend for the minimum value.