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

An accurate study of a floating offshore wind turbine (FOWT) system requires 16 interdisciplinary knowledge about wind turbine aerodynamics, floating platform 17 hydrodynamics and mooring line dynamics, as well as interaction between these 18 discipline areas. Computational Fluid Dynamics (CFD) provides a new means of 19 analysing a fully coupled fluid-structure interaction (FSI) system in a detailed manner. 20 In this paper, a numerical tool based on the open source CFD toolbox OpenFOAM for 21 application to FOWTs will be described. Various benchmark cases are first modelled 22 to demonstrate the capability of the tool. The OC4 DeepCWind semi-submersible 23 FOWT model is then investigated under different operating conditions. 24 With this tool, the effects of the dynamic motions of the floating platform on the wind 25 turbine aerodynamic performance and the impact of the wind turbine aerodynamics 26 on the behaviour of the floating platform and on the mooring system responses are 27 examined. The present results provide quantitative information of three-dimensional 28 FSI that may complement related experimental studies. In addition, CFD modelling 29 enables the detailed quantitative analysis of the wind turbine flow field, the pressure 30 distribution along blades and their effects on the wind turbine aerodynamics and the 31 hydrodynamics of the floating structure, which is difficult to carry out experimentally

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Most fatigue loaded structural components are subjected to variable amplitude loads which must be processed into a form that is compatible with design life calculations. Rainflow counting allows individual stress cycles to be identified where they form a closed stress-strain hysteresis loop within a random signal, but inevitably leaves a residue of open data points which must be post-processed. Comparison is made between conventional methods of processing the residue data points, which may be non-conservative, and a more versatile method, presented by Amzallag et al. (1994), which allows transition cycles to be processed accurately. This paper presents an analytical proof of the method presented by Amzallag et al. The impact of residue processing on fatigue calculations is demonstrated through the application and comparison of the different techniques in two case studies using long term, high resolution data sets. The most significance is found when the load process results in a slowly varying mean stress which is not fully accounted for by traditional Rainflow counting methods