本文主要是利用三維源點分佈法來預測三體船等速航行於規則波中時，穩態勢流與非穩態勢流之偶合效應，有關穩態勢流的部份是使用三維平移型源點求解，非穩態勢流的部份是利用三維脈動型源點。
首先利用小板法將船體浸水表面劃分成許多四角形小板，在四角形的小板上分佈源點，求解源點強度及壓力分佈，進而求得穩態興波與非穩態之船體運動問題，以及兩者之偶合效應同時也可求出沿船側之相對波高範圍，可供預測船首以及連接副船體甲板上水機率參考。
本文除計算之結果外，並於拖航水槽進行實驗驗證，探討不同副船體配置下穩態效應的影響，由結果看來，考慮穩態項之結果的確較符合實驗之趨勢，且由計算結果中發現，穩態項在某些情況下對於三體船之運動有明顯的影響，如在高速、長波、斜浪中之縱搖、橫移和橫擺運動。

In the paper, the motions of the trimaran ship, with coupled effect of steady flow potential and unsteady potential, advancing in regular wave are studied. The three dimensional pulsating source is applied to solve the unsteady potential which is needed for diffraction and radiation problems and the translating source is used solve the steady flow potential. With the unsteady and steady potentials, the related resultant pressure field, resultant wave elevation and coupled motions are obtained. In order to verify the validity of the present method, the experiments for the resistance and motions for the trimaran ship in head sea are also handled in NCKU towing tank. After comparisons, the results reveal that the method used in the present paper is acceptable except some discrepancies. The steady flow potential indeed affects the unsteady motions of the trimaran ship, especially for pitch, sway and yaw motions at high speed in long waves. The present study calculates not only the effect of the steady flow on the unsteady motion, but also the relative elevation which is very important to the trimaran ship while concerning the impact on the connected deck between the main hull and side hull. Therefore the prediction method developed in the present paper can be regarded as a useful tool to analyze the related hydrodynamic problem of the trimaran ship more deeply.

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