Estimation of the Drag Force and Frictional Resistance of a ship, using numerical modeling & Experimental Evaluation Results

Specification of the drag force values of a vessel in water can be considered as the first and most fundamental step in controlling the optimum fuel consumption of a ship due to high fuel costs and necessity of compliance with the marine environmental legislation. Using the numerical method and CFX software, for the first time, drag force and frictional resistance values of a scale model of a VLCC were calculated. The numerical calculation of the drag force value of the model was performed at five different speeds ranging from 0.65 to 0.85 m/s. The peculiar distinction between the present study and other similar studies is the selection of the speed and draft values of the model based on the actual ship servicing conditions. The results of the tests performed on the scale model in the towing tank were compared with those of the numerical model. Based on the performed verifications in the drafts with the size of 8 and 16.5 cm, the minimum and maximum values of the difference between the drag force values obtained from the laboratory and numerical models in the Froude numbers within the range of 0.13-0.16 were 3.5% and 15.4%, respectively.The minimum and maximum ratios of the frictional resistance to the total ship resistance were 85% and 93%, respectively. The results of the present study have been used to estimate the effect of the physical factors of the sea environment on the frictional resistance, speed, and fuel consumption of the vessel in the real sea condition.