Predicting the propulsive power of ships with high accuracy still remains a challenge. Well established practices in the 1978 ITTC Power Prediction method have been questioned such as the form factor approach and its determination method. This paper investigates the possibility to improve the power predictions by the introduction of a combined CFD/EFD Method where the experimental determination of form factor is replaced by double body RANS computations. Following the Quality Assurance Procedure proposed by ITTC, a best practice guideline has been derived for the CFD based form factor determination method by applying systematic variations to the CFD set-ups. Following the verification and validation of the CFD based form factor method in model scale, the full scale speed-power-rpm relations between large number of speed trials and full scale predictions using the CFD based form factors in combination with ITTC-57 line and numerical friction lines are investigated. It is observed that the usage of CFD based form factors improves the predictions in general and no deterioration is noted within the limits of this study. Therefore, the combination of EFD and CFD is expected to provide immediate improvements to the 1978 ITTC Performance Prediction Method.

中文翻译：

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基于CFD / EFD组合方法的CFD形状因子的验证和确认

高精度地预测船舶的推进力仍然是一个挑战。人们对1978年ITTC功率预测方法中公认的实践提出了质疑，例如形状因数法及其确定方法。本文研究了通过引入CFD / EFD组合方法来改善功率预测的可能性，该方法通过用双体RANS计算代替形状系数的实验确定。遵循ITTC提出的质量保证程序，通过对CFD设置应用系统变化，得出了基于CFD的形状因子确定方法的最佳实践指南。在以模型规模对基于CFD的尺寸因子方法进行验证和确认之后，利用基于CFD的形状因数结合ITTC-57线和数值摩擦线，研究了大量速度试验与满量程预测之间的满量程速度-功率-转速关系。可以看出，基于CFD的形状因数的使用总体上改善了预测，并且在本研究的范围内未发现任何恶化。因此，EFD和CFD的组合有望对1978年ITTC性能预测方法提供立即改进。