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題 名 | Time Domain Simulation of Data Buoy Motion=資料浮標運動之時序列模擬 |
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作 者 | 黃明志; | 書刊名 | Proceedings of the National Science Council : Part A, Physical Science and Engineering |
卷 期 | 22:6 1998.11[民87.11] |
頁 次 | 頁820-830 |
分類號 | 441.1 |
關鍵詞 | 資料浮標運動; 時序列模擬; Data buoy; Numerical simulation; Wave tank experiment; |
語 文 | 英文(English) |
中文摘要 | 資料浮標所量測之起伏運動加速度受下列因素影響:加速度計型式〔固定式或垂 直穩定式〕,加速度計位置,浮標縱搖運動,電子雜訊與數位化處理時之各項誤差,而導致 在低頻部份具有極不合理之能量。本文旨在時序列上模擬資料浮標在規則波與不規則波下之 動態運動以探討其起伏運動加速度在低頻部份之各種非線性成因。 研究所得結論為浮標起伏運動在示性波高小的模擬海況下並不具有低頻非線性共振效應 ,但浮標縱縱搖運動因非線性頻譜轉移之機制,已具有強烈之非線性共振效應,固定式加速 度計即會產生偽造的低頻加速度能量。浮標起伏運動在示性波高變大的模擬海況下已具有部 份之非線性共振效應,浮標縱搖運動之非線性共振效應更為強烈,水平穩定式加速度計即會 產生部份之偽造低頻加速度能量。在實用上採用水平穩定式加速度計比固定式加速度計可以 降低在低頻部份之偽造加速度能量。因浮標運動之非線性頻譜轉移機制而產生之偽造低頻加 速度能量,我們採用一雜訊修正函數之經驗公式加以修正後即可得到合理之轉換波譜。此雜 訊修正函數為一頻率之直線公式,其斜率與修正範圍可由不規則波浮標運動數值計算模擬與 現場觀測波浪數據分析而得。 |
英文摘要 | The measured heave motion in a data buoy system is influenced by the type of accelerometer used (hull-fixed or vertically stabilized), the position of the accelerometer, the pitch response of the buoy itself, electronic noise and digitized error in analysis. These various effects introduce spurious energy into the acceleration spectrum, particularly at low frequencies. In this study, numerical time domain simulation of data buoy motions in regular and irregular waves was conducted to study the various effects of nonlinearity on measured heave acceleration at low frequencies. The results of detailed studies indicate that in low sea-states, nonlinear pitch spectral transfer is the main mechanism which causes fixed accelerometer measurements to contain low-frequency spurious energy. For more severe sea-states, both nonlinear pitch and heave spectral transfer can introduce low-frequency spurious energy into stabilized accelerometer measurements. Simulation results also indicate that the stabilized accelerometer is preferred over the fixed accelerometer to reduce spurious energy at low frequencies. This spurious energy induced by nonlinear buoy motions can be effectively corrected by an empirical noise correction function which varies linearly with the wave frequency. The slope of this noise correction function which varies linearly with wave frequency. The slope of this noise correction equation and the frequency range of correction can be found from detailed numerical simulations and field measurements. |
本系統中英文摘要資訊取自各篇刊載內容。