圓柱單管搭配減搖裝置耐海性能實驗之研究

Abstract

本研究採用圓柱單管搭配不同的減搖裝置進行自由衰減實驗及不同波浪條件下的耐海性能實驗，減搖裝置包含不同直徑的擴盤及不同直徑與長度的擴管。自由衰減實驗結果找出自然頻率，再計算出各不同組合的附加質量、附加轉動慣性矩及阻尼比。再進行波浪中的耐海性能實驗，由量測結果計算起伏、俯仰及縱移運動的反應振幅運算子。 自由衰減實驗結果顯示擴盤及擴管會降低自然頻率、增加附加質量、增加附加轉動慣性矩及增加阻尼比。擴盤及擴管的起伏附加質量在直徑比1.6時為圓柱單管起伏附加質量的4倍及4.5倍，直徑比1.4擴管之起伏附加質量在長度30公分及10公分時相差14％，擴管俯仰附加轉動慣性矩在直徑比1.6時為圓柱單管的1.28倍。 耐海性能實驗結果顯示安裝擴盤及擴管後可以有效降低其起伏及俯仰反應振幅運算子，且直徑越大效果越顯著，對於起伏之效果優於俯仰。直徑比1.6之擴盤可將起伏反應振幅運算子降低57%及俯仰反應振幅運算子降低52%，直徑比1.6之擴管可將起伏反應振幅運算子降低46%及俯仰反應振幅運算子降低57%，就擴管長度而言長度30公分對比10公分之擴管可將起伏反應振幅運算子降低18%及俯仰反應振幅運算子降低14%。

In this study, the free decay test and the seakeeping test with different wave conditions were conducted by using a circular cylinder with different decay devices. The decay devices consist of different diameters of heave plates, different diameters and different lengths of enlarged cylinders. The natural frequency, added mass, added moment inertia and damping ratio can be obtained from the free decay test. The response amplitude operators of heave, pitch, and surge can be calculated from the seakeeping test with different wave conditions. The test results of the free decay tests show that the heave plates and enlarged cylinders can reduce the natural frequency of heave and pitch. The heave plates and enlarged cylinders can increase the added mass, the added moment inertia and the damping ratio of heave and pitch. The heave added mass of the heave plate of 1.6 diameter ratio is 4 times more than the heave added mass of the circular cylinder. The heave added mass of the enlarged cylinder of 1.6 diameter ratio is 4.5 times more than the added mass of the circular cylinder. The difference of the heave added mass of the enlarged cylinder of 1.4 diameter ratio between the length of 30 cm and 10 cm is 14%. The added moment inertia of the enlarged cylinder of 1.6 diameter ratio is 1.28 times more than the added moment inertia of circular cylinder. The test results of the seakeeping test show that the heave plate and enlarged cylinder can effectively reduce the response amplitude operator （RAO） of heave and pitch. The larger diameter ratio is more effective, and the reduction of heave RAO is better than pitch RAO. The heave plate of 1.6 diameter ratio can reduce 57% of the heave RAO and reduce 52% of the pitch RAO. The enlarged cylinder of 1.6 diameter ratio can reduce 46% of the heave RAO and 57% of the pitch RAO. The enlarged cylinder of 30cm length can reduce 18% of the heave RAO and 14% of the pitch RAO of the enlarged cylinder of 10cm length.