This paper proposes a Computational Fluid Dynamics (CFD) based unsteady RANS model which enables the prediction of the effect of marine coatings and biofouling on ship resistance and presents CFD simulations of the roughness effects on the resistance and effective power of the full-scale 3D KRISO Container Ship (KCS) hull. Initially, a roughness function model representing a typical coating and different fouling conditions was developed by using the roughness functions given in the literature. This model then was employed in the wall-function of the CFD software and the effects of a typical as applied coating and different fouling conditions on the frictional resistance of flat plates representing the KCS were predicted for a design speed of 24 knots and a slow steaming speed of 19 knots using the proposed CFD model. The roughness effects of such conditions on the resistance components and effective power of the full-scale 3D KCS model were then predicted at the same speeds. The resulting frictional resistance values of the present study were then compared with each other and with results obtained using the similarity law analysis. The increase in the effective power of the full-scale KCS hull was predicted to be 18.1% for a deteriorated coating or light slime whereas that due to heavy slime was predicted to be 38% at a ship speed of 24 knots. In addition, it was observed that the wave resistance and wave systems are significantly affected by the hull roughness and hence viscosity

It is critical to be able to estimate a ship׳s response to waves, since the resulting added resistance and loss of speed may cause delays or course alterations, with consequent financial repercussions. Slow steaming has recently become a popular approach for commercial vessels, as a way of reducing fuel consumption, and therefore operating costs, in the current economic and regulatory climate. Traditional methods for the study of ship motions are based on potential flow theory and cannot incorporate viscous effects. Fortunately, unsteady Reynolds-Averaged Navier–Stokes computations are capable of incorporating both viscous and rotational effects in the flow and free surface waves. The key objective of this study is to perform a fully nonlinear unsteady RANS simulation to predict the ship motions and added resistance of a full scale KRISO Container Ship model, and to estimate the increase in effective power and fuel consumption due to its operation in waves. The analyses are performed at design and slow steaming speeds, covering a range of regular head waves, using a commercial RANS solver. The results are validated against available experimental data and are found to be in good agreement with the experiments. Also, the results are compared to those from potential theory

Predictions of added resistance and the effective power of ships were made for varying barnacle fouling conditions. A series of towing tests was carried out using flat plates covered with artificial barnacles. The tests were designed to allow the examination of the effects of barnacle height and percentage coverage on the resistance and effective power of ships. The drag coefficients and roughness function values were evaluated for the flat plates. The roughness effects of the fouling conditions on the ships' frictional resistances were predicted. Added resistance diagrams were then plotted using these predictions, and powering penalties for these ships were calculated using the diagrams generated. The results indicate that the effect of barnacle size is significant, since a 10% coverage of barnacles each 5 mm in height caused a similar level of added power requirements to a 50% coverage of barnacles each 1.25 mm in height.

To reduce the fuel consumption and greenhouse gas emissions of ships, it is necessary to understand the ship resistance. In this context, understanding the effect of surface roughness on the frictional resistance is of particular importance since the skin friction, which often takes a large portion in ship drag, increases with surface roughness. Although a large number of studies have been carried out since the age of William Froude, understanding the roughness effect is yet challenging due to its unique feature in scaling. In this study, a Computational Fluid Dynamics (CFD) based unsteady Reynolds Averaged Navier-Stokes (RANS) resistance simulation model was developed to predict the effect of barnacle fouling mainly on the resistance and hull wake characteristics of the full-scale KRISO container ship (KCS) hull. Initially, a roughness function model was employed in the wallfunction of the CFD software to represent the surface conditions of barnacle fouling. A validation study was carried out involving the model-scale flat plate simulation, and then the same approach was applied in full-scale flat plate simulation and full-scale 3D KCS hull simulation for predicting the effect of barnacle fouling. The increase in frictional resistance due to the different fouling conditions were predicted and compared with the results obtained using the boundary layer similarity law analysis of Granville. Also, a further investigation of the roughness effect on the residuary resistance, viscous pressure resistance and wave making resistance was carried out. Finally, the roughness effect on the wave profile, pressure distribution along the hull, velocity distribution around the hull and wake flows were examined.

The fuel consumption of a ship is strongly influenced by her frictional resistance, which is directly affected by the roughness of the hull׳s surface. Increased hull roughness leads to increased frictional resistance, causing higher fuel consumption and CO2 emissions. It would therefore be very beneficial to be able to accurately predict the effects of roughness on resistance. This paper proposes a Computational Fluid Dynamics (CFD) model which enables the prediction of the effect of antifouling coatings on frictional resistance. It also outlines details of CFD simulations of resistance tests on coated plates in a towing tank. Initially, roughness functions and roughness Reynolds numbers for several antifouling coatings were evaluated using an indirect method. Following this, the most suitable roughness function model for the coatings was employed in the wall-function of the CFD software. CFD simulations of towing tests were then performed and the results were validated against the experimental data given in the literature. Finally, the effects of antifouling coatings on the frictional resistance of a tanker were predicted using the validated CFD model