排水型單體船在規則波頂浪條件下 船舶運動及阻力預測

Abstract

本研究對單體船在規則波中頂浪條件下的耐波性能進行數值模擬，探討波高、波浪周期以及船速對附加阻力以及起伏和縱搖運動響應的影響。船舶在波浪中的弗勞德數為0.13、0.26、0.40，波形尖銳度範圍為0.0087至0.0306，無因次化波長範圍為0.42至於1.70，所預測的附加阻力係數範圍為0.1至2.2。本研究採用基於勢流理論的朗肯源小板法進行時域計算，並考慮黏性效應以提高數值預測的準確性。在黏性流模擬中，雷諾數落在7.58×10^7至2.26×10^8間。計算結果顯示，運動反應振幅運動算子隨波長增加而增大，在15節船速下增長最為顯著，而黏性效應通常較小，僅在特定的遇浪週期及高波高條件下有明顯影響。隨著船速增加，附加阻力的峰值位置向長波長方向移動，與線性波浪理論的預測不一致。在波高為0.875米時，特別是縱搖運動，非線性行為變得顯著。此時艉部因為形成高壓區域，增強縱搖力矩的非線性效應，但對於起伏力的非線性影響較小。

This study presents the prediction of seakeeping performance of a mono–hull vessel in regular head seas, emphasizing the dependence of added resistance and heave and pitch motion responses on wave height, wave period, and ship speed. The ship is operating at three Froude numbers, i.e., 0.13, 0.26, and 0.40, where the wave steepness is selected from 0.0076 to 0.0306, and the dimensionless wavelength is chosen from 0.41 to 1.70. The predicted added resistance coefficient varies between 0.1 and 2.2. Numerical simulations are conducted using a time–domain Rankine source panel method based on a fully nonlinear theory, where viscous damping effects are also incorporated via a CFD method. The Reynolds numbers are ranged from 7.58×10^7 to 2.26×10^8 in the CFD simulation. The RAOs increase with wavelength, showing the steepest growth at 15 kn, while damping effects become nontrivial at specific encounter periods and high wave heights. The wavelength of the added resistance peaks grows as the ship speed increases, deviating from linear wave theory predictions. Nonlinear behavior becomes evident at high wave heights, particularly in pitch motion, where the calculation without damping corrections may underestimate responses. A high–pressure region forms at the stern when wave height is at 0.875 m, delivering higher nonlinearity of pitch moment than that of heave force. The predicted results emphasize the limitations of linear theory and the necessity of advanced methods, such as CFD, to accurately account for nonlinear and viscous effects.