使用 OpenFOAM 嵌套網格技術模擬具穩定翼SWATH船形靜水航行性能預測

Abstract

本研究採用計算流體力學軟體OpenFOAM，預測具穩定翼小水面雙體船在靜水條件下的阻力，並著重於探討穩定翼對水動力特性的影響。本研究為了預估在達到平浮所需的穩定翼攻角，將作用於小水面雙體船的縱搖力矩拆成船殼、後穩定翼和前穩定翼三個部分的貢獻。本研究使用OpenFOAM中的OverInterDymFoam求解器，結合嵌套網格、自由液面模型和動態網格，使用SST k-ω紊流模型，剛體運動則使用Newmark方法，預測小水面雙體船在自由液面上的運動響應。計算結果顯示，透過比較不同速度的總阻力與波形特徵，證實本方法可有效預測SWATH於靜水中的航行性能。本研究首先是以固定姿態探討在不同速度下預測達成平浮姿態所需的穩定翼攻角；另外是同時考慮起伏與俯仰兩自由度，預測穩定翼對運動響應的影響。結果顯示，預測穩定翼平衡攻角時，應考慮船體對流場的影響。此外，穩定翼除能平衡縱搖並產生附加阻力外，在高速下亦會引發額外下沉力與起伏運動。固定姿態與2-DOF模擬之總阻力比較顯示，高速時若忽略姿態變化，將導致可達約15%的總阻力低估，凸顯航行姿態對總阻力預測的重要性。

This study utilizes OpenFOAM to simulate the resistance performance of a Small Waterplane Area Twin Hull (SWATH) vessel equipped with stabilizing fins under calm water condition. This research focuses on the vessel’s altitude contributed by the stabilizing fins. To estimate the angle of attack of the stabilizing fin required for achieving pitch equilibrium, the total pitch moment acting on the SWATH vessel is decomposed into contributions from the hull, aft fin, and fore fin. The simulations are conducted using the OverInterDyMFoam solver, incorporating overset mesh technique, free surface model, and dynamic mesh capability to predict the vessel’s hydrodynamic response in calm water. The turbulence effect is modeled using the SST k-ω turbulence model, and the rigid body motion is solved using the Newmark method. Validation results show that this approach reliably predicts SWATH performance in calm water by comparing total resistance and wave patterns at various speeds. This study performs two types of simulations. One uses a fixed attitude to assess stabilizing fin effects and estimate the attack angle for zero trim angle, and the other allows heave and pitch motions (2-DOF) to evaluate motion response. The results show that hull effects on the flow field must be considered when predicting the equilibrium angle of stabilizing fins. At high speeds, the fins not only balance pitch and add resistance but also cause extra heave force and heave motion. Comparison between fixed attitude and 2 DOF cases shows that neglecting attitude can underestimate total resistance by up to 15 %, highlighting the importance of attitude in resistance prediction.