TaidaFloat半潛式浮臺耐海性能試驗之研究

Abstract

本研究建立了一個1/100 TaidaFloat半潛式浮臺的縮尺模型，該浮臺是由底部的三個浮筒連接三個不對稱的六角柱所組成，並搭配一個3x3的懸鍊式繫泊系統。為了解浮臺的運動特性，針對縮尺模型進行了自由衰減運動及耐海性能試驗，根據自由衰減試驗的結果確定了模型在六個自由度下的自然頻率和阻尼比。並且在六個自由度中又分別進行了在不同的初始速度值的自由衰減運動試驗，以了解不同初始速度對於阻尼比的影響，由結果顯示在六個自由度中，阻尼比與不同初速度皆大致呈線性關係。透過耐海性能試驗可以求得六個自由度的反應振幅運算子(Response Amplitude Operator, RAO)，而在本試驗中於5種浪向下進行規則波與不規則波條件的耐海性能試驗，浪向分別為0°、45°、90°、135°和180°。在規則波條件的耐海性能試驗結果顯示，縱移(Surge)、橫移(Sway)、起伏(Heave)、平擺(Yaw)的RAO均會隨著波浪頻率降低而逐漸增加，另外縱移在波浪頻率約為0.74Hz時有一局部峰值是由俯仰(Pitch)的自然頻率所誘導。同樣橫移也會在橫搖(Roll)的自然頻率附近誘導出局部的峰值。在不規則波的耐海性能試驗結果顯示，六自由度都會在其自然頻率上產生明顯的峰值，同時也會受到非規則波浪中央頻率範圍，約為0.6Hz~0.9Hz，而產生較明顯的RAO局部峰值。此外在不規則波試驗中產生了拍擊現象，使得在橫搖和平擺的倍數自然頻率上被激發出較大的RAO局部峰值。在綜合考量了規則波與不規則的耐海性能試驗的結果後，發現在浪向45°時，浮臺整體的運動反應較小，因此日後欲在臺灣海峽上安裝浮臺時，選擇浪向45°是較為理想的狀態。

In this study, a scaled-down model of a 1/100 TaidaFloat semi-submersible floating platform was constructed. The floating platform comprises three asymmetric hexagonal columns connected by three pontoons at the bottom, and it is equipped with a 3x3 catenary mooring system. To investigate the motion characteristics of the floating platform, experiments on free decay motion and seakeeping performance were conducted using the scaled model. The natural frequencies and damping ratios of the model’s six degrees of freedom were determined based on the results of the free decay experiments. Moreover, experiments were conducted to observe the free decay motion at different initial velocity values for each degree of freedom (DOF), aiming to assess the impact of various initial velocities on the damping ratio, which showed a roughly linear relationship. The six degrees of freedom Response Amplitude Operator (RAO) can be obtained through the seakeeping performance experiment. The experiments were conducted under regular wave and irregular wave conditions, encompassing five wave directions: 0°, 45°, 90°, 135°, and 180°. In regular wave experiments, RAO values for surge, sway, heave, and yaw increased as wave frequency decreased. Notably, a local peak surge value appeared at a wave frequency of approximately 0.74 Hz due to the pitch-induced surge. Similarly, sway exhibited a local peak value near the natural frequency of roll. As for the seakeeping performance experiments involving irregular waves, obvious peaks were observed at the natural frequencies of all six degrees of freedom. These degrees of freedom were also influenced by the peak frequency of the irregular waves, which was approximately 0.6 Hz to 0.9 Hz, resulting in local RAO peak values. Additionally, the irregular wave experiments induced a slamming phenomenon, leading to local RAO peak values at the multiples of the natural frequencies of roll and yaw. After considering the results of seakeeping performance experiments with regular and irregular waves, it was observed that the floating platform exhibits smaller motion response at a wave direction of 45°. Therefore, for future installations in the Taiwan Strait, a wave direction of 45° is recommended for optimal performance.