以真實尺度模擬週期波於泥質海床上過風機基座

Abstract

本研究使用計算流體力學軟體OpenFOAM，模擬台灣離岸風電單樁式基礎在泥質海床與週期波浪的交互作用，為了模擬較真實的情況，查閱台灣離岸風電相關文獻，取得設計波浪條件、基樁直徑及土壤參數，使用雙黏性流體及牛頓流體簡化描述泥的運動行為。過去研究多關注於砂質海床，較少泥質海床的研究，因此本研究針對泥質海床深入探討。研究成果顯示，圓柱附近泥水交界面以上有小部分的水流速會被泥影響，使流速發生減速甚至回流的現象。不考慮泥床影響將低估負x方向的圓柱水平作用力，高估正x方向的圓柱水平作用力，而圓柱的俯仰力矩將隨著水平受力上升或下降，兩者趨勢相同。泥質海床與砂質海床兩者在圓柱周圍的沖刷深度量級相近。這些研究結果可以提供台灣離岸風電或其他海洋工程參考。

This study is based on the computational fluid dynamics software OpenFOAM to simulate the interaction between a monopile foundation and a muddy seabed under periodic waves in Taiwan. To capture more realistic conditions, relevant literature on offshore wind energy in Taiwan is reviewed to obtain design wave conditions, pile diameter, and soil parameters. The motion of mud is simplified using the bi-viscous and Newtonian models. Most of the existing research has focused on sandy seabeds, with limited studies on muddy seabeds. Consequently, this study focuses on muddy seabeds. Here we show that near the cylinder and above the mud-water interface, a small portion of the water flow is influenced by the mud, resulting in a deceleration or even reversal flow. Neglecting the influence of the mud bed would underestimate the negative horizontal force acting on the cylinder and overestimate the positive horizontal force in the x-direction. The pitching moment of the cylinder will increase or decrease with the horizontal force, following a similar trend. The order of scour depth magnitude around cylinder between muddy and sandy seabeds is the same. These research results can provides reference for Taiwan's offshore wind and other marine engineering structures.