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A reliable investigation which allows an accurate prediction on seakeeping performance of a monotricat ship in head-seas is obviously required. To achieve this objective, a Computational Fluid Dynamic simulation approach is proposed by looking into attainable outcomes with precision, whilst a hydrodynamic description that is underlying the rationale behind the results is explained. Two conditions of the monotricat ship model, termed as with and without stepped-hull, were employed in the computational simulation. Several wave properties, such as various wavelengths and wave heights on heaving and pitching performances associated with different Froude number (Fr) were taken into account. The results showed that the increase of Fr was proportional with the increase the heaving and pitching motions. These led to the downgrade seakeeping performances presented in the form of high Response Amplitude Operators (RAO). In shorter wavelengths (λ<1), RAO of the heave and pitch motions were insignificant. However, the subsequent increase of wavelength (λ>1) was proportional with the increased RAO of the heave and pitch motions. The further increase in wavelength (>1.75) resulted in less RAO both of the heave and pitch motions. The increase in wave height had affected a proportionate increase in the heave and pitch motions that may possibly lead to degrade her seakeeping quality. It can be concluded that the effects of Fr and wavelength on the heave and pitch motions of the monotricat ship had more complex phenomenon as compared to the wave-height ones. These CFD results are useful as preliminary prediction for navigation safety during sailing.

Prediction of the seakeeping performance of a ship in the earlier ship's design step is necessary to ensure the safety of navigation during sailing. To accommodate such a demand, this research proposes to analyse the seakeeping performance of a rounded hull catamaran. The vertical motion of the catamaran including the heave and pitch motions were quantified by her Response of Amplitude Operator (RAO). The Computational Fluid Dynamic software was used to develop the model, where several effects of various Froude numbers, hull lateral separation ratios and wavelengths on the heave, and pitch motions of the rounded hull catamaran have been taken into account. The results revealed that the higher Froude number associated with less hull lateral separation ratio was proportional to the subsequent increase of her heave and pitch motions. In the case of / ≤1.0, the seakeeping quality of the rounded hull catamaran has been improved and presented in the form of a sufficient reduction of the heave and pitch motions. It is shown that the estimated seakeeping performance of the rounded hull catamaran greatly depends on the Froude numbers and magnitude of wavelength.

A reliable investigation that allows an accurate prediction of the total resistance coefficient of a high-speed" deep-V" catamaran in shallow water is obviously required. The Computational Fluid Dynamic simulation proposed approach is aimed to attain this precise outcome, while a hydrodynamic description of the rationale underlying behind the results is explained. Several effects of lateral separation ratios (S/L) and longitudinal staggered position (R/L) against a wide range of Froude numbers (Fr) from 0.5 to 1.0 were considered. The results revealed that the general increase in Fr is proportional to the increase of total resistance. In contrast, the increase of lateral separation ratios dealt with less total resistance coefficient, where the sufficient reduction of C T was about 11% as the Fr increase from 0.5 to 0.6 for S/L=0.3. Regardless of R/L ratios, the results showed the subsequent increase of Fr from 0.5 to 1.0 was also proportional to the total resistance, where the maximum increase of RT was about 21% as the Fr increase from 0.6 to 0.7. In addition, the increase of R/L ratios has led to sufficient increment of C T by 1.5% as the Fr increase from 0.9 to 1.0. Generally, the increase of S/L and R/L ratios have similar effects on the total resistance characteristics. This CFD simulation results are very useful as preliminary data for the ship resistance, which is mainly required for predicting a ship powering accurately.

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