標題: 應用波壓推算水位變化之研究
Water Surface Elevation Recovery from Wave Pressure Signals
作者: 唐世澤
Tang, Shih-Tse
郭一羽, 邱永芳
Yi-Yu Kuo, Yung-Fang Chiu
土木工程學系
關鍵字: 轉換函數;TF
公開日期: 1995
摘要: 本研究利用 Kuo and Chiu(1994)所提出波高與波壓之經驗轉換函數,
配合快速傅立 葉轉換法(FFT),由水下壓力計所測得之波壓訊號,來推
算水位變化。將 Nielsen(1986)所提出之局部頻率法(LCM)及本文所使用
之快速傅立葉變換法, 同時對不同的波高與波壓間的轉換關係,做比較
分析。研究結果發現,在波壓計放 置深度較淺時,利用 FFT法與 LCM法
經由經驗轉換函數皆可準確的做變換,但隨著 壓力計放置的位置愈深時
,使用經驗轉換函數與 FFT法,將可得到較佳的準確性。 本文同時也針
對 FFT法中,截斷頻率無法明確判定的問題,提出簡易而明確的判斷 方
式。 此外本文也藉由物理模型試驗,探討淺水域中波壓與波高的轉換關
係。經由 實驗數據分析後發現,淺水域中波浪分裂所造成高階成份的波
壓能量與波高能量間 的轉換函數,與以往的研究一樣,主要的是與一個
由角頻率及波壓計 設置深度組合而成的無因次參數有關,且各階成份波
的轉換函數似乎一樣。此由規則 波實驗數據所迴歸的經驗轉換公式,經
由單一方向不規則波的驗證,證明此經驗轉換 公式可利用來做淺水域中
波壓與波高的變換。
In the present study an empirical transfer function between
the wave pressure and wave height,which was established by Kuo
and Chiu(1994) ,was applied to predict the history signals of
the free water surface elevation from the wave pressure beneath
the still water level.The Fast Fourier Transform(FFT) method is
used to calculate the power spectral and history signals of
wave height.The FFT method is compared with LCM method
developed by Nielsen(1986) in this paper.It is found that both
of FFT method and LCM method are accurately calculated when the
pressure gages are locatted near the still water level.However,
when the distance between the pressure gage and the still water
level is longer,the FFT method with the empirical transfer
function is more efficient and accurate than the LCM method.
Furtherwore,the present study has decided on the cutoff
frequency range,the weak point of the power spectral analisis
which was resolved in this paper. Furthermore,the present study
used the physical model test to investigate the transfer
function between the wave pressure and the wave height in
shallow water. By the analysis from the experimental data, we
can find the transfer function is concern with the wave
frequency and pressure gage locations. In addition ,the
transfer functions of each older nonlinear components seem to
be the same.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT840015054
http://hdl.handle.net/11536/60009
顯示於類別:畢業論文