穩態勢流對波浪中雙體船之非穩態運動之混合效應

The Combined Effect of the Steady Potential on the Unsteady Motions of Twin-Hull Ship in Waves

In the present paper, the three-dimensional source distribution method including the coupled effect of the steady flow potential and unsteady potential is applied to predict the twin-hull ship motions in regular waves. The pulsating source and translating source are adopted to solve the corresponding unsteady potential and steady potential respectively. The unsteady ship motion prediction is usually made by neglecting the steady potential to solve the corresponding hydrodynamic forces under the assumptions of high frequency and low speed. However the steady potential might have significant influence on twin-hull ship motions because of the interactions between two hulls. Therefore it is included in the present calculation of the corresponding hydrodynamic pressure and forces, and the combined effects on six degrees freedom of motions are then investigated. The results calculated in the present study reveal that the combined effect on the unsteady motions due to the steady flow potential are indeed significant for some modes of motions of the twin-hull ship especially for pitch and yaw motions with high speed in long waves. 在本文中利用三維之源點分佈法來預測規則波中之雙體船之運動，其中包含了穩態勢流與非穩態勢流之混合影響。非穩態勢流所採用之源點為脈動型源點，而穩態勢流則採用移動型源點。一般在計算非穩態運動時均在高頻低速之假設下，並省略穩態勢流來做分析。然而由於雙體船之兩船殼之交互影響，此穩態勢流之混合效應可能變得很明顯。因此在本文中加以考慮，並以交度運動結果來檢視其效應。結果顯示穩態勢流的確對雙體船之某些運動影響很大，特別是在高速、長波中之縱搖與橫擺運動。