Development of a small-sized tanker with reduced greenhouse gas emission under in-service condition based on CFD simulation

Abstract

In the present study, the hull form and appendage of a 6.5 k DWT tanker was improved to reduce greenhouse gas emissions in the in-service navigation condition. The conventional hull form of the 6.5 k DWT tanker has been designed in terms of performance in the ideal condition of a calm-sea. On the contrary, the performance of a ship in the in-service condition should take the added resistance due to wind and waves in the real sea into consideration. In order to reduce the added resistance due to waves, the bow hull form was modified to have a sharper entrance with increased length between perpendiculars. This was intended to ensure that the waves follow the curved bow surface more smoothly, thereby reducing the added resistance due to waves. The stern hull form was also modified to have V-shaped section shapes to reduce viscous pressure resistance. In addition, the flow control fins were optimized in terms of position and angle of attack. The added resistance of the resulting hull form was then analyzed numerically in regular wave with a varying wavelength ratio λ/Lpp=0.5∼2.0. The added resistance in regular waves was subsequently integrated with respect to the wavelength to obtain the added resistance in irregular waves. Finally, by combining it with the sea state occurrence probability, the daily fuel oil consumption (DFOC) was able to be calculated for the actual in-service routes for the tanker. The entire process of hull form modification and evaluation was conducted with free-surface CFD simulation in the presence of regular waves. A series of model tests was undertaken to confirm the improvements of the optimal hull form over the original in terms of performance in waves as well as calm-sea performance. The resulting DFOC and daily CO2 emissions for the optimal hull form in the in-service conditions was found to be reduced by 14.8%. Furthermore, the calm-sea DFOC and CO2 emissions were also improved by 15.6%.