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The ship propulsion characteristics are commonly obtained by means of towing tank tests. The experimentally obtained results need to be extrapolated to full-scale using extrapolation procedures, which may introduce numerous sources of errors. Alternatively, Computational Fluid Dynamics (CFD) can be used to assess the ship hydrodynamic performance. Nowadays, with increased computational power it is possible to conduct full-scale numerical simulations [1], which allow the prediction of scale effects. In this study, the scale effects on the propulsion characteristics are investigated by performing numerical simulations of the self-propulsion and resistance tests using the commercial software package STAR-CCM+. The Japan Bulk Carrier (JBC) is selected for the case study since experimental results are available online [2]. The mathematical model used within the numerical simulations is based on Reynolds-Averaged Navier Stokes (RANS) equations which are discretized using the Finite Volume Method (FVM). The Volume of Fluid (VOF) method is used to locate and track the free surface with the High-Resolution Interface Capturing scheme applied to maintain a sharp interface between the fluids. Within STAR-CCM+ the motion of the ship is modelled using the Dynamic Fluid Body Interaction (DFBI) method, which enables six degrees of freedom. The body force propeller method, which is based on a uniform distribution of volume force over the cylindrical virtual disk, is used to model the effects of the propeller. The rotation rate and delivered power are determined using the numerical simulations of the self-propulsion test. The scale effects on the thrust deduction fraction and effective wake are investigated. The nominal wake of the ship is obtained using the International Towing Tank Conference (ITTC) procedure [3] within numerical simulations of the resistance test. A verification study is conducted to assess the simulation numerical uncertainty and the validation study is carried out using the available experimental results to confirm the validity of the numerical model. The obtained numerical results present the scale effects on the ship propulsion characteristics. As noticed in [4], significant scale effects are obtained for both the integral value of nominal wake and circumferential averaged non-dimensional axial velocity distribution.

In this paper, an artificial neural network was used to predict the added resistance coefficient for container ships in regular head waves for various speeds. The data used for training the neural network were gathered based on performed numerical calculations using the Boundary Integral Element Method for various hull forms of container ships. The numerically obtained results were validated against the available experimental data for three benchmark container ships. The data were divided into three classes based on the ship length, and the expressions for the prediction of the added resistance coefficient for each container ship class were provided. The performance and generalization properties of the neural network were evaluated based on the normalized value of the root mean square error. The model enables reliable prediction of the added resistance coefficient within the preliminary design stage of a ship based on the ship characteristics and speed.

Nowadays maritime industry is focused on reduction of greenhouse gas (GHG) emissions from shipping. Alt-hough about 2.89 % of the total global anthropogenic CO2 emissions comes from shipping industry, in 2018 the International Maritime Organization (IMO) adopted the strategy to lower the total annual GHG emissions by at least 50 % by 2050, in comparison to 2008. Different measures to mitigate the emissions are proposed and used in the shipping industry, which can be classified into technological and operational measures. The use of alternative fuels and renewable energy sources could be considered as a third category of mitigation measures. One of the short-term operational measures that is being implemented in maritime transport is slow steaming. It is a low- cost measure that can greatly reduce the emissions since fuel consumption depends on the sailing speed. However, it is important to investigate whether the savings in fuel consumption due to lower sailing speed can exceed the costs of a higher number of vessels that have to be engaged to keep the yearly transport work constant. The ship operators would gladly implement this measure if the savings achieved by speed reduction would be greater than the capital and operating costs.

The shipping industry is responsible for the emission of approximately 940 million tonnes of CO2 annually, which is at least 2.5% of the world’s total CO2 emissions. New regulations encourage the shipping industry to take measures to increase the energy efficiency of ships to reduce greenhouse gas emissions. Therefore, the International Maritime Organization (IMO) has proposed several short, medium, and long-term measures for the shipping industry to reduce these emissions by 50% by 2050. Trim optimization is one of the simple short-term measures for achieving the fuel savings recommended by the IMO as it does not require any hull modification or marine engine upgrades. Traditionally, the ship hull is optimized for the design speed and draft. However, during its lifetime the ship sails at different speeds and drafts, and for certain combinations, a significant reduction in fuel consumption could be achieved. In this paper, numerical simulations of resistance test for a 6750–TEU container ship in full scale are carried out at different trim angles using Computational Fluid Dynamics (CFD). Numerical simulations are performed to determine the optimal trim with the lowest value of the total resistance. A verification study is performed for grid density and time step to determine the total numerical uncertainty. Furthermore, the obtained results of the numerical simulations are validated against the extrapolated results of the model tests. The flow around the ship hull, shear stress distribution on the wetted surface, wave patterns, and hydrodynamic pressure distribution are analysed for different trim angles. Finally, the recommendation for the optimal trim at the design speed is given.

Biofouling attaches at immersed surfaces in between hull cleaning. Containerships are usually fouled with biofilm due to their duty cycle related to high speed and short immobile periods in ports. Fouling with biofilm is commonly neglected during ship operation since it is commonly assumed that it does not affect ship hydrodynamic performance significantly. In this paper, the impact of biofilm on the energy efficiency of the Post Panamax and Post Panamax Plus containership fleets while sailing in the Adriatic Sea is assessed. The investigation is performed for real environmental conditions that a containership can encounter on a typical sailing route passing through the Adriatic Sea. Thus, the impact of waves and wind is taken into account based on mean values of significant wave height and wind speed for containerships sailing at the design speed along the analysed route. The procedure for the assessment of the detrimental effects of biofilm on the energy efficiency of containerships is proposed, and the potential fuel consumption and carbon dioxide emissions savings related to hull cleaning are determined and discussed. The proposed procedure includes the determination of calm water resistance by the Holtrop and Mennen method, the added resistance in waves by Liu and Papanikolaou’s method and spectral analysis using the Tabain’s spectrum for the Adriatic Sea, the wind resistance by the Blendermann method and added resistance due to biofouling using the Granville method. The obtained results demonstrate the significance of hull cleaning from an environmental point of view indicating the detrimental effects of biofilm.

For accurate prediction of the ship hydrodynamic characteristics by means of numerical simulations, it is important to determine the numerical and modelling errors. In this paper, the flow around a Post-Panamax 6750 TEU containership in full scale is simulated using Computational Fluid Dynamics (CFD). Within the numerical simulations of the resistance test, the influence of different numerical parameters on the total resistance and free surface elevation is assessed using different turbulence models. The numerical parameters included in this study are time step and discretization schemes for spatial and temporal discretization. The verification study of the results obtained from the numerical simulations is carried out using the Grid Convergence Index (GCI) method. The presented data consists of total resistance, free surface elevation, trim and sinkage data.

In this study numerical assessment of nominal wake for the Japan Bulk Carrier at model scale is carried out. Numerical simulations based on Reynolds Averaged Navier-Stokes equations are carried out with k − ω SST and k − ε turbulence model. The verification study is carried out and the numerical uncertainty in the prediction of a nominal wake is determined. The validation study is performed by comparison of the obtained results with the experimental data from the literature. It is demonstrated that Computational Fluid Dynamics can be a valuable tool in the assessment of nominal wake.

U ovom diplomskom radu izrađen je linearni model gibanja jedrilice (nalik Grob G-103 Twin Astiru). Izračunati su svi potrebni aerodinamčki koeficijenti koristeći se nacrtom jedrilice iz priručnika održavanja te aproksimacijom aeroprofila repnih površina i pojednostavljenom geometrijom trupa. Nakon provjerene ravnotežnog leta i stabilnosti, cijeli model jedrilice je implementiran u simulacijsku platformu s modelom sa šest stupnjeva slobode gibanja. Model je izrađen pomoću MATLAB programskog paketa i Simulinka. Uz model jedrilice izrađeni su modeli instrumenata pomoću programskog paketa VAPS XT te su spojeni sa Simulink modelom. U radu je pokazana njihova izrada te njihova implementacija u simulacijsku platformu. Simulator pokreće FlightGear programski paket za vizualizaciju leta. U simulaciji je uključen i pilot koji zadaje upravljačke veličine pomoću upravljačke palice. In this thesis a motion model of a sailplane (resembling Grob G-103 Twin Astir) is made. The aerodynamic coefficients have been calculated with the available information and with approximations of the unknown values. After the stable flight conditions and stability have been checked, the whole model of the sailplane was implemented in a simulation platform with six degrees of freedom. Model has been created with the use of MATLAB and Simulink. Alongside the sailplane model, instrument models have been made with the use of VAPS XT software aswell as the connection with Simulink model. In this thesis the designing process of the instruments is shown and their implementation in the simulation platform. Simulator runs FlightGear as the main software for the visualization of the flight.

U radu se promatra tanki, savitljivi, dvodimenzijski aeroprofl. Aeroprofl se deformira pod utjecajem aerodinamičkih sila. One su izjednačene s membranskim silama koje djeluju samo tangencijalno na aeroprofl. Korištena je linearna analiza kao metoda rješavanja problema. Problem je riješen analitički te su rezultati dobiveni pomoću konačnog broja jednadžbi. Na taj način rezultati nisu egzaktni, ali su dovoljno blizu analitičkom rješenju. In this paper, a thin, deformable two-dimensional aeroprofle is observed. The aeroprofle is deformed by the aerodynamic forces. These forces are then balanced with tension forces. A linear analysis has been used to resolve the problem of such airfoils. The problem is solved by analytical methods but the results displayed have been calculated with a fnite number of equations. Because of this, the results are not exact but they are much closer than needed.