打樁噪音氣泡(球)幕減噪三維聲場模擬研究

近年跳電事件頻傳，能源備轉容量率持續下降，電該從何來是一個大哉問，而台灣海峽及台灣西部近海有絕佳的風場，極具開發離岸風力發電場之價值，長期來看風力發電成為重點發展的項目已是必然。然而離岸風機建置基礎打樁時會產生巨大之低頻噪音，可能影響海洋哺乳類的生態，需在打樁施工時進行噪音隔離或採用降噪措施，減輕離岸風場開發對於海洋生態之衝擊。本研究使用COMSOL Multiphysics多重物理量耦合分析軟體，來進行衝擊式打樁噪音減噪模擬研究，建立三維模型將氣泡幕及氣球幕之減噪效益在頻域進行分析，從而進行打樁噪聲的預估，以台灣西部海域21號示範風機為模型進行模擬計算，建立一結合噪聲預估及減噪預測之數值模型。本研究分析打樁噪聲能量於的20Hz-100Hz頻率的減噪效果，除了三維模型外亦建立二維軸對稱模型，兩者的減噪效益差異相當大，並將計算結果實海域量測結果比對，三維模型更近似實驗量測結果，同時也做了氣球幕及氣泡幕減噪效益分析，兩模型之減噪效益差異不大，在多數情況下可以互相替換，另也比較在相同氣球尺寸下體積分率及氣球幕放置位置對減噪效益之影響，以建立不同氣泡幕於不同頻段之插入損失，預估打樁噪音經減噪後於750公尺處是否超過法律規範之160 dB re 1 μPa2s。

關鍵字

有限元素法；打樁噪音；減噪效益；氣泡幕；氣球幕；插入損失

並列摘要

In recent years, there have been frequent power outages, and the energy Percent Operating Reserve has steady decline. It is an essential question for politicians to answer where the power would come from. The Taiwan Strait and the western coast of Taiwan have excellent wind farms, which are extremely valuable for developing offshore wind farms. Wind power has inevitably become a critical development project. However, the offshore wind turbine will generate huge low-frequency noise when piling the foundation, which may affect the ecology of marine mammals. Noise isolation or noise reduction measures should be taken during piling construction to reduce the impact of offshore wind farm development on marine ecology. This study uses the COMSOL Multiphysics multi-physics coupling analysis software to conduct simulation research on noise reduction of impact piling noise. The three-dimensional model is built to analyze the noise reduction effect of the bubble curtain and the balloon curtain in the frequency domain to predict the pile driving noise. The No. 21 demonstration wind turbine in the western waters of Taiwan was simulated and calculated for the model. This study also analyzes the noise reduction effect of piling noise energy at frequencies 20Hz-100Hz. In addition to the three-dimensional model, a two-dimensional axisymmetric model is also established. The noise reduction effect of the two is quite different. The calculated results are compared with the actual sea area measurement results. The three-dimensional model is more similar to the experimental measurement results, and the noise reduction benefits of the balloon and the bubble curtains are also analyzed. The noise reduction benefits of the two models are not significantly different. In most cases, they can be replaced with each other. The effect of volume fraction and balloon curtain placement on noise reduction efficiency, to establish the insertion loss of different bubble curtains in various frequency bands, and to estimate whether the piling noise exceeds the legal specification of 160 dB re 1 μPa2s at 750 meters after noise reduction.