Comparison of Pressure Transfer Functions

波壓轉換函數之比較

黃明志(Min-Chih Huang)

《海洋工程學刊》 1卷1期 (2001/11) Pp. 23-34

https://doi.org/10.6266/JCOE.2001.0101.01

摘要

利用水下壓力計來量測波浪已行之有年，惟欲求得準確之結果則需一適當的波浪與波壓轉換函數。本文首先回顧往昔學者所採用之各種波壓轉換函數公式並描述探討其特點，其中之一為波壓轉換函數除了與一個無因次頻率參數有關外，亦與壓力計設置水深息息相關。換言之，波壓轉換函數為相對水深與無因次壓力計水深二者之函數。此與郭、邱(1994)波壓轉換函數經驗公式只與無因次頻率參數有關之結論相反。
此外本文亦探討其它可行之雜訊修正法，以避免壓力譜轉換為波譜時在高頻部分之波譜極度放大。本文並利用現場量測波壓數據，比較線性波浪理論、非線性波浪理論、線性波浪理論與修正因子、及郭、邱(1994)波壓轉換函數經驗公式等反算所得之波譜，可見波壓轉換函數經驗公式所得結果與其它三種理論方法之結果差距太大，不符常理。我們建議在未來之研究中波壓轉換函數經驗公式應如Baqerizo and Losada(1995)所述，依不同之壓力計水深參數而變化。

關鍵字

波壓轉換函數 ； 雜訊修正法

並列摘要

Measurement of surface water waves with subsurface pressure transducer has been employed over the last five decades. However adequate pressure transfer function relating wave and pressure amplitudes is required to yield accurate results. Previous formulas of pressure transfer function are reviewed first in this paper and important characteristics of pressure transfer function are delineated. Among these characteristics, we show a strong dependency of pressure transfer function on the frequency parameter and also on pressure transducer submergence parameter, i.e., the pressure transfer function is a function of both relative depth and transducer submergence parameter. This is contrary to the conclusion of Kuo and Chiu (1994) where the empirical formula for the pressure transfer function is independent of transducer submergence parameter.
Alternative noise correction methods are also studied in this paper in order to avoid excess high-frequency wave spectrum components when converting from the pressure spectrum. Field pressure data are then used to calculate the wave spectrum using linear and nonlinear transfer functions, linear transfer function with correction factor, and empirical formula of Kuo and Chiu (1994). Considerable and unreasonable difference exists between empirical formula and the other three theoretical formulations. We therefore recommend that in future studies the empirical transfer function should be grouped in small range of transducer submergence parameter as suggested by Baqerizo and Losada (1995).

並列關鍵字

pressure transfer function ； noise correlation method