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    Title: 二維方柱橫向與扭轉向振動耦合之氣動力研究
    Other Titles: Aerodynamic forces of a square prism in transverse and torsional coupled motion
    Authors: 呂宜靜;Lu, Yi-ching
    Contributors: 淡江大學水資源及環境工程學系碩士班
    盧博堅;Lu, Po-chien
    Keywords: 二維方柱;強制振動;頻率比;偏心量;A square prism;forced vibration;ratio of frequency;eccentricity
    Date: 2005
    Issue Date: 2010-01-11 07:29:12 (UTC+8)
    Abstract: 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.
    Appears in Collections:[Graduate Institute & Department of Water Resources and Environmental Engineering] Thesis

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