振動式打樁水下噪音模擬研究

Abstract

近年來全世界各國對於離岸風力發電場之開發日益興盛，全世界排名前20處離岸風場當中臺灣西部海域就擁有超過一半的絕佳風場，因此具有極大的開發潛力，在未來幾年時間離岸風力發電場之開發數量會不斷增加。離岸風力發電場之發展在過去十年中不斷突破與創新，因此離岸風力發電機組設計尺寸、離岸距離以及基礎安裝水深都不斷地增加。離岸風力機組在安裝樁基礎時，這些基樁安裝期間通常會產生巨大之低頻噪音導致於水下噪音過高，可能影響海洋哺乳類的生態從而危害水生生物。因此本研究將依據現今臺灣評估離岸風機打樁噪音的方式，使用有限元素法於頻率域下模擬振動式打樁工法並進行打樁噪音之預估，建立一套振動式打樁噪聲預估之數值模型。 本研究分成兩部分，第一部分是使用COMSOL Multiphysics有限元素法數值分析軟體來執行振動式打樁工法水下噪音模擬研究，建立三維模型並輸入振動打樁之力道函數在頻率域進行模擬分析，從而執行該打樁工法噪音預估，並且分析該工法噪音能量介於1 Hz至500 Hz頻率之結果，與實際量測案例進行比對後，驗證其可行性與準確性。第二部分是為了讓三維模型更貼近實際打樁需求並且減少模型計算時間，也透過該模擬方法亦建立不同簡化型式的三維模型，經噪音結果比對後差異不大。此模擬方法可用來預估振動式打樁工法水下噪音聲源強度，可當作日後離岸風力發電場開發之參考來源。

In recent years, there has been a growing global interest in the development of offshore wind farms, and Taiwan''s western waters rank among the top 20 offshore wind sites worldwide, boasting more than half of the ideal wind resources. Consequently, it holds significant development potential, and the number of offshore wind farms is expected to continually increase in the coming years. The development of offshore wind farms has witnessed continuous breakthroughs and innovations over the past decade, leading to an increase in the design size of offshore wind turbine generators, offshore distances, and foundation installation water depths. During the installation of pile foundations for offshore wind turbines, the piling process typically generates significant low-frequency noise, resulting in elevated underwater noise levels. This may potentially impact the ecology of marine mammals and pose a threat to aquatic life. Therefore, this study follows the current Taiwanese approach for evaluating the pile-driving noise of offshore wind turbines. It utilizes the finite element method to simulate vibratory pile driving in the frequency domain and predict pile-driving noise, establishing a numerical model for the estimation of vibratory pile-driving noise. The study is divided into two parts. The first part utilizes the COMSOL Multiphysics finite element analysis software to conduct numerical simulations of underwater noise generated by vibratory pile driving. A three-dimensional model is established, and the force function of vibratory pile driving is input for frequency domain simulation analysis to predict the noise. The results, ranging from 1 Hz to 500 Hz, are compared with actual measurement cases to validate feasibility and accuracy. The second part aims to make the three-dimensional model more realistic and reduce computational time. Various simplified forms of the three-dimensional model are established through this simulation method, and the differences in noise results are found to be minimal after comparison. This simulation method can be used to predict the underwater noise source intensity of vibratory pile driving, serving as a reference for future offshore wind farm developments.