雙體船阻力預估與干涉效應之研究

Abstract

本文研究的主要目的，是經由雙體船船模試驗的結果，探討雙體船之阻力干涉效應，並進行阻力預估。 本研究首先以Insel與Molland[12]在南漢普敦大學進行的雙體船船模試驗結果為基礎，瞭解雙體船在不同佛勞德數與船體間距下，其黏性干涉與興波干涉對船舶阻力性能之影響。 本研究採用穿浪式雙體船船形，由阻力試驗結果比較，來探討雙體船之干涉現象，證明雙體船的船體間距，如Insel與Molland[12]所提，的確存在著干涉效應。及使用具有拋物線線型之韋格里船形，除了可觀察到船體間距對雙體船的阻力性能影響之外，並經由試驗的結果，求得黏性干涉因子與興波干涉因子，並以佛勞德氏與形狀因子之方法進行實船阻力預估。由試驗結果發現穿浪式雙體船在兩船間距比S/L大於0.4及韋格里船形S/L大於0.7時即沒有阻力干涉。同時發現阻力干涉的現象是因兩船的艏波在兩船間交會，產生較大的波高引起雙體船的運動姿勢變化，而產生阻力的變化，甚至產生阻力係數低於單體的阻力係數即所謂的負干涉。 最後，經由計算流體力學的興波阻力比較，顯示在中速度域計算的趨勢大致吻合，唯計算所得的興波阻力係數略低於試驗所得的興波阻力係數。並以Insel與Molland[12]的韋格里船形試驗結果作驗證，比較在形狀因子、黏性干涉因子與興波干涉因子的預估結果，由比較結果發現，若能準確地量得低速的船模阻力試驗值，即可求得正確的形狀因子及可計算正確的實船阻力預估值。

The purpose of this research is to study the powering prediction and resistance interference effects of catamaran from ship model test results. First, the viscous interference and wave-making interference of catamaran with the parameters of Froude number and the separation of the demihull were studied based on experimental results by Insel and Molland[12]. At first, the wave-piercing catamaran model was used to study the interference effects by ship model test. The test results show that there exist interference effects between the demihull of catamaran as shown in the tested results of Insel and Molland[12]. Following, the Wigley hull form, which has parabola geometry, was used to study the detailed interference effects of catamaran. The resistance performance with different separation distance between demihull was measured and the viscous interference and wave-making interference were also calculated from the test results. The full scale resistance of the catamaran was predicted by Froude’s method and form factor method. It is found that there is no interference effect if the non-dimensional separation distance S/L is greater than 0.4 for the wave-piercing catamaran and 0.7 for the Wigly hull form. The interference effect is due to the sinkage and running trim changed caused by the buoyancy changed from the interaction of two bow waves meeting in the channel between the demihulls. The negative interference of resistance is also due the changed of the sinkage and running trim. Finally, through the comparison between the calculated results and test results, it is found that the trend of the calculated wave-making resistance is the same as that of tested. But, the value of calculated wave-making resistance is a little bit smaller than the tested wave-making resistance. The values of form factor, viscous interference and wave-making interference of Wigly were verified with that of Insel and Molland[12]. It is found that if the resistance of low speed could be measured accurately, than the form factor could be determined accurately and the full scale resistance could be predicted accurately.