Ship roll damping is a key factor for predicting large amplitude roll motions, such as para-metric roll and stability under dead ship condition. In this paper, the free roll motions of an interna-tional standard model ship 2792 for dead ship are simulated based on the unsteady RANS equation in calm water by two types of meshes, the sliding mesh and the overset mesh. The free roll decay curves of numerical simulations are compared with experimental results, and the roll damping coeffi-cients are also compared with that in Ikeda's simplified formula. The calculated free decay curves a-gree quite well with the free decay curves from the experiments, and the errors of roll damping co-efficient calculated by CFD are smaller than that from Ikeda's simplified formula, which validate that the unsteady RANS equation can be used to predict roll damping.%船舶横摇阻尼是影响参数横摇和瘫船稳性等大幅横摇运动的关键参数.文中基于非定常RANS方程在静水中对模型2792进行了自由横摇衰减的数值模拟,该模型是船舶第二代完整稳性衡准制定中瘫船稳性研究的国际标准船模,数值模拟中采用了两种网格类型,一种是滑移网格,另一种重叠网格.计算结果表明,数值模拟的自由横摇衰减曲线和模型试验结果吻合良好,另外CFD计算的横摇阻尼与试验值的误差小于Ikeda's经验公式计算的误差,证明非定常RANS方程可用于预报横摇阻尼.
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