云林海域之稳定风浪频谱  

Steady-state Wind Wave Spectrum off Yun-Lin, Taiwan

作　　者：黃煌煇(Hwung-Hweng Hwung) 江文山(Wen-Son Chiang) 廖顯仁(Hsien-Jen Liao) 

出　　处：《海洋工程學刊》

摘　　要：本文引用在云林海域南侧之波浪观测桩进行约一年的长期波浪观测记录探讨此海域之波谱特性。根据筛选出符合稳定风场条件之单峰风浪频谱，利用非线性回归分析，分别与JONSWAP波谱、TMA波谱及修正型JONSWAP波谱进行套配，发现以修正型JONSWAP波谱形式较符合此海域稳定风场条件之单峰风浪波谱。由波谱形状参数与波浪无因次化参数之相关性分析，显示波谱之能量尺度参数与波浪尖锐度在双对数座标系统上呈线性正相关；波谱之尖峰系数与波浪尖锐度呈负相关之趋势。再由符合单峰风浪波谱之正规化波谱分析，得知此海域之波谱随风速减小逐渐接近饱和波谱形式；然在大风速条件下，由於稳定吹风延时、风域及水深等影响，因此波谱偏离饱和状态。This paper investigates the characteristics of locally typical wave spectrum by using the long term measurements of wave climate at the offshore area of Yun-Lin Industrial District. A set of criteria was proposed to complete the selection of quasi steady-state wind wave spectrum. The locally typical wave spectrum formulation was established by fitting parameters of JONSWAP, TMA, and modified JONSWAP spectrum with non-linear least square method. The fitted parameters indicate that the energy scaling parameter, a in JONSWAP and β in modified JONSWAP, linearly increases as wave steepness increases in log scale. In contrast, the peak enhancement parameter, γ in JONSWAP and γ(subscript d) in modified JONSWAP, linearly decreases as wave steepness increases. The comparisons between measured spectrum and fitted empirical spectrums show that the modified JONSWAP spectrum was best- fit to the measured wave spectrum. The normalized wave spectrums were gradually approaching to the fully developed sea state as wind speed decreases. However, due to the limitations of fetch and duration of wind blowing, the development of wind wave spectrum deviated from the saturated state for high wind speed.

关 键 词：波譜 單峰 穩定風場