New horizons in marine coatings

Marine biofouling is an increasing problem from both economic and environmental points of view in terms of increased resistance, increased fuel consumption, increased GHG emissions and transportation of harmful non-indigenous species. Marine coatings are prevalently used to mitigate biofouling and smooth the surfaces of hulls. This paper aims at introducing new horizons and novel approaches in marine antifouling coatings. Firstly, marine biofouling and fouling prevention methods are briefly introduced. Afterwards, latest research in coating/fouling hydrodynamics is presented. Biomimetic approach to antifouling technology, bio-inspired antifouling strategies and the challenges in designing bio-inspired antifouling coatings are then discussed in detail. It is believed that, the on-going research in marine coatings will lead to an effective mitigation of marine biofouling while maintaining the harmony between man-made structures and marine life

On the importance of antifouling coatings regarding ship resistance and powering

This paper aims to introduce one of the latest investigations on development of marine antifouling coatings and also to demonstrate the importance of the type of antifouling coatings on fouling accumulation and ship resistance/powering. First, marine biofouling and fouling prevention methods are reviewed. A recent research study (EU FP7 FOUL-X-SPEL Project) concerning a novel and environmentally friendly antifouling coating is presented and discussed. Next, a case study is carried out to assess the effect of fouling on ship resistance and powering. A vessel is selected and the roughness on the hull surface induced by different level of fouling is considered. The increase in frictional resistance and effective power is evaluated for each particular case by using boundary layer similarity law analysis and experimental data. The results emphasise that the type of antifouling coatings has a great importance on the amount of fouling accumulation, hence on ship performance especially in low speed

Predicting the effect of biofouling on ship resistance using CFD

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

Experimental determination of added hydrodynamic resistance caused by marine biofouling on ships

This paper presents a novel experimental approach towards establishing a method to predict the added resistance caused by the calcareous fouling. An extensive series of towing tests using the flat plates covered with artificial, 3D printed barnacles were carried out at the Kelvin Hydrodynamics Laboratory (KHL) at the University of Strathclyde. The tests were designed to examine the effects of 2 different fouling parameters, namely the coverage percentage and locations of the fouling accumulation, over a range of Reynolds numbers. The paper presents the added resistance due to calcareous fouling in terms of added frictional coefficient for a surface coverage of fouling for up to 20%, and for a surface coverage of different spatial heterogeneous fouling for a constant 5% over different speeds (Reynold numbers)

An investigation into the effect of biofouling on the ship hydrodynamic characteristics using CFD

To reduce the fuel consumption and green-house 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 wall-function 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 predictedand 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

AN OVERVIEW OF MARINE CORROSION PROTECTION WITH A FOCUS ON CATHODIC PROTECTION AND COATINGS

Corrosion is the gradual deterioration of a material or its properties through a chemical reaction with its environment. There are several methods of preventing a material from corroding. Cathodic protection (CP) and coatings are very popular methods for corrosion protection. Each individual method has its own benefits and drawbacks, whereas experience has shown that the most effective method of corrosion prevention is a combination of both CP and coatings. This combination can provide very good protection over a long period of time. This paper focuses on the combined use of both CP and coatings for ships. Calculation of a CP design is explained briefly and the factors affecting the choice of the type of CP system are demonstrated. Then, a sample anode plan of a ship is shown. Finally, the calculation of a cathodic protection system of a ship is presented using data provided by coating manufacturers and shipyards

Experimental determination of added hydrodynamic resistance caused by marine biofouling on ships

An extensive series of towing tests using flat plates covered with artificial barnacles were carried out at the Kelvin Hydrodynamics Laboratory (KHL) at the University of Strathclyde. The tests were designed to examine the effect of the coverage percentage of barnacles on the resistance and effective power of ships, over a range of Reynolds numbers. This paper presents the added resistances due to calcareous fouling in terms of the added frictional resistance coefficient for a surface coverage of fouling of up to 20%, over different speeds (Reynolds numbers). The drag coefficients and roughness function values of each surface were evaluated. Roughness effects of the given fouling conditions on the frictional resistances of an LNG tanker were then predicted for different ship speeds using an in-house code which was developed based on the similarity law analysis of Granville (1958). Added resistance diagrams were then plotted using these predictions. Finally, powering penalties of the LNG tanker were predicted using the generated diagrams

Experimental determination of added resistance due to barnacle fouling on ships by using 3D printed barnacles

3D printed artificial barnacles were attached on flat plates and towed over a range of Reynolds numbers in order to be able to calculate added resistance and power requirements of ships due to calcareous fouling. Since barnacle fouling occurs naturally it is possible to observe the barnacles in different sizes on any randomly selected ship surface. To model this condition three different barnacle sizes were selected and used to represent growing stages of the attached barnacles. The flat plates were covered with barnacles within a range of 10% to 50% area coverage respectively and towed over different speeds at the Kelvin Hydrodynamics Laboratory in the University of Strathclyde. Frictional resistance coefficients and roughness function values were then calculated for each surface based on experimental results. Roughness effects of the given fouling conditions on the frictional resistances were then predicted for a bulk carrier ship using an in-house code developed based on boundary layer similarity law analysis. Added resistance diagrams were plotted using these predictions. Finally, the increase in the frictional resistance and powering penalties of the ship were predicted using the generated diagrams

Scale effect on ship resistance components and form factor

To design eco-friendly ships, the hydrodynamic behaviour of the hull has to be estimated precisely. The first and foremost one is the ship resistance, which is closely related to the energy efficiency of the ship. Different extrapolation methods, based on different assumptions, have been used to predict the full-scale ship resistance from model-scale experiments. In this manner, it is important to understand the scale effect on the individual ship resistance components. In this study, URANS CFD simulations of KCS and KVLCC2 were conducted at different scales. The total resistance components were decomposed into the individual resistance components to investigate the scale effects. The simulation results were compared with full-scale resistance predictions using different extrapolation methods and the rationale of the different compliances between them was investigated. Finally, the hydrodynamic characteristics in different scales were examined