It is critical to be able to estimate a ship's response to waves, since the resulting added resis... more 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.
Corrosion is the gradual deterioration of a material or its properties through a chemical reactio... more 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.
ABSTRACT The fuel consumption of a ship is strongly influenced by her frictional resistance, whic... more ABSTRACT 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.
It is critical to be able to estimate a ship's response to waves, since the resulting added resis... more 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.
Corrosion is the gradual deterioration of a material or its properties through a chemical reactio... more 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.
ABSTRACT The fuel consumption of a ship is strongly influenced by her frictional resistance, whic... more ABSTRACT 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.
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Papers by Yigit Demirel