In this study, cavitating flow modeling around the Delft hydrofoil by using Computational Fluid Dynamics (CFD) is presented. In this context, 2 different cavitating flow conditions are simulated around the 3-D Delft hydrofoil. Drag force, lift force, cavitation volume on the hydrofoil and cavitation pattern are obtained. The results achieved from the CFD analysis are validated by the cavitation tunnel test results as well as by the results of various numerical analysis studies obtained from the literature. In order to model the cavitation accurately with CFD, all properties of cavitating flows such as turbulence, unsteady pressure and velocity fluctuations, two-phase flow, mass transfer from liquid phase to vapor phase, three-dimensionality, viscosity, dynamics of cavitation bubbles and interactions between bubbles should be included in the solution at the same time. In this study, cavitating flow is simulated by using various models for the aforementioned properties by means of rapidly developing computational technology. Three-dimensional, unsteady cavitating flow around the hydrofoil was solved by Detached Eddy Simulation (DES) technique with SST Menter k-? turbulence model. Two phase flow is modelled by Volume of Fluid (VOF) method. Cavitation was modelled by Schnerr-Sauer cavitation model which solves the simplified Rayleigh-Plesset bubble equation to model cavitation. In the analysis, simulations were carried out with normal meshes at first. Thus the regions where high pressure and velocity fluctuations and cavitation occur are determined. Then the mesh is refined in that regions. Eventually, in the regions where high pressure and velocity fluctuations and cavitation occur, have better mesh resolution. Also, the mesh density in all computational domain is increased and the mesh is modified that is appropriate for DES model. In this way, the computational errors related to the mesh which is a very important parameter in the CFD studies, has been minimized. In addition, the analysis are repeated with three systematically refined meshes and three different time steps. Using the results obtained from these analysis, it is shown that the study is independent of grid and time. The numerical uncertainties of the analysis in the simulated flow conditions are calculated.

Shipbuilding has a quite complex product value chain with design, procurement, construction, outfitting, painting, assembly, assessment, and trials. These processes and related activities are executed in general within restricted periods adhering to specific milestones. Each year many occupational accidents and diseases are encountered at this dangerous branch of industry resulting in not only dramatic non-fatal injuries and deaths but also financial losses. The Fourth Industrial Revolution comprises autonomous production robots also called “cyber-physical systems” that are capable of making decisions utilizing Internet of Things (IoT) and big data analysis, incorporation of widespread, fully integrated, automatic, and optimized production management philosophy and realization of the Idea “Smart Factory”. This new paradigm has the potential to change the nature of shipbuilding just like any other industrial branch and is expected to be a nexus to new solutions for neutralizing occupational risks faced during shipbuilding processes.

There are several methods for ship resistance calculations. Computational Fluid Dynamics (CFD) applications, other numerical methods, experimental and statistical methods are the mainly used methods. Resistance are calculated at different velocities and ship operation conditions to get an optimum hydrodynamic form. Therefore, the ship resistance calculation method should be suitable for a systematic and repetitive application. Due to these reasons, the CFD method is used widely for ship resistance calculations. It has been possible to calculate total resistance for ships with the developing computer technologies. However, calculation of total ship resistance with CFD still requires high calculation capacity and long calculation times. Generally, ship resistance calculations with CFD are performed at model scale. Model resistance is then extrapolated to full ship scale. International Towing Tank Conference (ITTC) 1957, Hughes-Prohaska and ITTC 1978 are the most common extrapolation techniques. Telfer’s GEOSIM (GEOmetrically SIMilar) method developed in the distant past is another technique for ship resistance problems. Total resistance coefficients of hulls are computed at different scale ratios. These models have geometric and kinematic (Froude) similarities. Non-dimensional resistance coefficients are then plotted against Reynolds numbers. After that the ship resistance at full scale is computed by a simple extrapolation technique. Unlike other methods, in the Telfer method, total ship resistance is not separated into its components. It is known that the Telfer method is a very successful method to predict the ship resistance. However, this method is expensive in experimental studies as it requires different scaled models to be produced and multiple model tests. In this study, resistance values have been calculated for a benchmark hull geometry, Duisburg Test Case (DTC) which is commonly used in computational ship hydrodynamics studies. In the beginning of CFD analyses, mesh independence studies were conducted for one single scale and the output was applied to the other scales in proportion with the model lenghts. It is aimed to calculate total ship resistance accurately without seperating it to its components. CFD computations are made on six different scaled models and total resistance coefficients are obtained for these models. In “Tefler Method” model tests are replaced by CFD analyses. Then the Tefler method is modified to enhance the accuracy.

The Maritime sector is a comprehensive branch of industry with its numerous fields of application and various operation processes. Because approximately 90% of world trade is via maritime trade, it plays an indispensable role on world trade network. Although the great capacity that maritime trading system can manage this high trade, the success of the system is strongly bound to some factors such as absolute punctuality, safety and cooperation of shareholders. Speed optimization, which has impacts on fuel consumption, flue gas emissions and general operation costs, is a multidimensional issue. The speed of a ship is optimized during design stage; however, in some cases, the designed speed may not be the optimal speed due to the time constraints. Although it is well known that speed reduction is an important way to reduce CO2 emissions, this method has some constraints as well. Speed optimization brings some uncertainties besides its remarkable benefits. Although it can be accepted as an important way to reduce emissions, it must be updated for every voyage and condition.

In this study, the hydroelastic vibration analysis of clamped rectangular plates vertically in contact with quiescent fluid is carried out. The method of analysis is divided into two parts; namely, in-vacuo and wet. Both in-vacuo and wet analyses are conducted by the novel isogeometric NURBS concept; the in-vacuo analysis is carried out by the isogeometric FEM, while, wet analyses are performed by the isogeometric BEM. In in-vacuo analysis, the Kirchhoff thin plate theory is adopted, and the isogeometric FEM formulation for Kirchhoff plate is presented. In wet analysis, fluid is assumed non-viscous and incompressible; the rotational motions of the fluid is neglected. It is also assumed that fluid actions and related pressure distribution over the structure only occur due to modal vibrations of the structure; in other words, it is assumed that both the elastic structure and the surrounding fluid has no forward speed. The linear hidroelasticity theory is adopted in order to determine the wet dynamic characteristics of the structure under the fluid-structure interaction forces. In-vacuo and wet dynamic characteristics (natural frequencies and corresponding mode shapes) are presented comparatively with the available analytical and experimental results in the literature. It is concluded that the present work demonstrates the versatility of the isogeometric analysis concept.

Blade element momentum (BEM) technique is a fast, simple and an efficient method applied to measure the performance of propeller. The traditional linear BEM method is based on the assumption that the drag has a little effect on the induced angle of attack and thus the induced angle of attack is very small at all sections along the blade. However, it is known that this approach creates inaccurate results especially on high advanced ratios. The Nonlinear BEM method avoids this inaccuracy arising from this negligence. In this paper, the open water performance of benchmark propeller DTMB 4381 has been investigated by using the nonlinear BEM and RANS methods. The results have been compared with the linear BEM method and experimental results.

In this study, the multi-criteria decision-making methods of fuzzy logic, fuzzy AHP, and fuzzy TOPSIS were utilized to determine the ideal class of ships that a specific shipyard can build during the decision-making stages of shipyards for them to be successful in the competitive environment of the world market. For this purpose, a general information and related literature are reported in the first chapter. Decision-making, decision-making methods, fuzzy logic, fuzzy decision methods, and the data obtained by the implementation are presented consecutively in the chapters that follow. In the last section, general results and evaluations obtained from the study are given. With the ever-evolving customer demands and differentiated ship types due to the development of technology and the importance given to the project management by shipbuilding companies, which are in an effort to maintain their place in the world shipbuilding market, is increasing. It is suggested that the companies, which would like to take the lead in project management within the shipbuilding sector, should adopt the decision-making and multi-criteria decision-making methods examined in this study and use these methods in every decision stage. The appropriate method will be integrated into every decision-making process and contributes to the improvement of processes and decisions.