台大浮式風機平台耐海性能實驗

Seakeeping Test of the TaidaFloat Offshore Floating Platform

本研究針對台大半潛式浮式風機平台進行自由衰減運動及耐海性能實驗，本研究只進行浮式平台本身之運動，風機的重量分佈在平台的三根六角柱上；本研究進行六自由度的自由衰減運動及耐海性能實驗，由自由衰減運動的實驗結果以最小平方法嵌合運動方程式的解，以求得自由衰減運動的自然頻率及阻尼比。並分別以不同初始值進行六自由衰減運動之實驗，以找出不同初始值與阻尼比的影響，由實驗結果顯示阻尼比與初速度約為線性關係。耐海性能實驗可求得浮式平台的六自由度反應振幅運算子(response amplitude operator，RAO)，由於縱移(surge)、橫移(sway)及平擺(yaw)的自然頻率低於0.3Hz，低於造波機可造波浪的頻率，無法進行實驗。耐海性能實驗結果顯示，縱移、橫移及起伏的RAO均隨著頻率降低而增加，縱移在無因次頻率1.40時有一局部高值是由俯仰的自然頻率所誘導。橫搖的RAO隨著波浪頻率接近自然頻率時而增加，但當波浪頻率越低時其RAO值卻更高，推論應是錨鍊拉力不對稱導致大波高條件下產生明顯的橫搖反應；俯仰的RAO在自然頻率時有最大值，但在無因次頻率0.8附近有一局部高值，推論是起伏運動所誘導，平擺的RAO隨著無因次頻率降低而增加趨勢合理。

The free decay and seakeeping model tests of the TaidaFloat offshore semi-submersible floating platform with a mooring system were conducted in this study. The weights of the wind turbine and tower were distributed uniformly among the three column supports. Free decay tests of six degrees of freedom, including surge, sway, heave, roll, pitch, and yaw, were conducted. The natural frequencies and damping ratios were derived from the free decay tests. The damping ratios of the six degrees of freedom are approximately linear with the initial velocity. Response amplitude operators of six degrees of freedom were obtained from the seakeeping tests. Seakeeping involves testing for surge, sway, and yaw cannot be conducted by the wavemaker when the wave frequency falls below 0.3Hz. The RAO of surge, sway, and heave increases as the wave frequency de-creases, according to the seakeeping test results. The surge RAO has a local maximum value at a non-dimensional frequency of 1.4, which is induced by pitch motion. The roll RAO increases as the frequency decreases, and it continues to increase as the frequency decreases further. It may be due to the unbalanced forces of the mooring lines in the long-wave conditions. The pitch RAO has a maximum value at the natural frequency, and there is a local maximum value at a non-dimensional frequency of 0.8, which is near the natural frequency of heave. The yaw RAO increases as the frequency of the wave decreases, which is a normal trend.