LEE- Açık Deniz Mühendisliği-Yüksek Lisans

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http://hdl.handle.net/11527/19188

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  • Öge
    Potential wind farm design in Western Black Sea region of Turkey
    (Graduate School, 2022-01-21) Gahramanov, Rahman ; Beji, Serdar ; 508181222 ; Offshore Engineering
    Today, wind energy has become one of the common types used to meet the ever-increasing need for electrical energy. Wind energy, which has zero carbon dioxide emissions compared to other classical types of electric power generation (coal, natural gas), is becoming more and more common. Especially offshore wind turbines are calculated more efficiently compared to onshore. This is due to the high wind speed at sea and the almost absence of obstacles that the wind may encounter. Developing countries such as Turkey need to spend large sums of money to meet their electrical energy needs. And a part of the electricity (26%) produced in Turkey is obtained from hydroelectric power plants, but this is not enough to guarantee the whole of Turkey with electrical energy. Most of Turkey's electricity generation (58%) is made with coal and natural gas. Only 15% of energy comes from wind turbines, geothermal and solar panels. As can be seen from the percentages, this is a major source of problems for Turkey, both economically and environmentally. Taking these into account, for a country surrounded by sea on 3 sides, turning to offshore wind turbines will provide great advantages for Turkey, both environmentally and economically. In this thesis, a potential wind farm design has been made in the western black sea region of Turkey. The design phase was made by taking these criteria into account: Technical (Wind speed and water depth), environmental (Bird migrations, ports and ship routes, fault lines, underwater cables, civil aviation, military regions, territorial water), social (Tourisim and fishery), logistics, grid connection, type of wind turbine and choosing layout. Comprehensive analyzes were made by taking these criteria into account. In addition, in this thesis, the situation of wind energy in the world and in Turkey, Turkey's wind energy potential has been investigated. Information was also shared on how the use of classical energy types and the use of hydroelectric power plants are harmful to nature. The model of the wind turbine was decided to be the Vestas production V174-9.5 MW™ (due tp logistical availability). In addition, annual energy production was calculated both in accordance with the number of wind turbines (99) calculated in accordance with the size of the area of the selected region, and by taking into account the wind speed. The power of the offshore wind farm is calculated to be 940 MW. Considering the depth, it was decided that the foundation of the wind turbine should be monopile. Finally, the total force and maximum momentum ( and = 152,417,746 ) to be applied to the monopile were determined by using the Morrison's equation, these calculations were based on the highest wind speed data of 30 years that (1978-2009) blowing from Şile to the selected region, obtained from the General Directorate of Meteorology of the Ministry of Environment and Forestry of the Republic of Turkey. The design of the wind farm has been done successfully.
  • Öge
    A generalized deep reinforcement learning based controller for heading keeping in waves
    (Graduate School, 2022-06-21) Beyazit, Afşin Baran ; Kınacı, Ömer ; 508191229 ; Offshore Engineering
    Reinforcement Learning (RL) is a machine learning method where a learner (the agent) tries to maximize a reward by learning how to act under different environmental circumstances. The agent looks at the state of its environment (through the state vector), takes an action, and then gets a reward and the next state of its environment. The agent improves its action-taking strategy (policy) with every action it experiments with. RL methods have been used for many decision-making problems including control problems with promising results. Unlike many traditional control methods, a model-free RL doesn't need any environment dynamics to operate. This is especially beneficial for problems where the model dynamics are non-linear or not well-known. However, classical controllers are still the most used method of control for maritime applications. Heading-keeping is a maritime control problem where a controller's objective is to keep the heading (yaw) angle of a vehicle constant. Generally speaking, the industry standard is to use traditional feedback controllers such as PID for this problem. This study focuses on designing a generalized RL controller for the heading-keeping problem in waves. The study compares the designed RL controller to a traditional controller in terms of yaw error and rudder usage and observes that the designed RL-based controller performs better than the used traditional controller. The first iterations of the RL agent had many issues. Unlike traditional controllers, the RL agents don't inherently recognize that in an idealized environment they can deal with waves coming from 0 and 180 degrees with almost zero rudder usage. On top of that, the first few developed agents had problems with excessive rudder usage, steady-state error, and overshooting behavior. All of these problems have been solved in the final iteration of the RL agent. Instead of just explaining the final agent, the thesis starts off with a weak RL agent and explains how it can be improved iteratively. This way the thesis explains how one might approach the problem of developing an RL-based controller. The first section focuses on giving a rough summary of RL and the problem case, explains the purpose of the thesis, then talks about previous work over marine movement control in literature. Some detailed information about the used tools and simulation environment is also given here. The second section introduces LQR controllers and designs an LQR controller for the heading keeping problem. The third section explains RL in-depth to lay the foundation for the upcoming sections. The fourth section starts with a naively designed simple RL agent and iteratively improves it. In each iteration of development, the agent is compared to the designed LQR controller, its weaknesses are analyzed, and the improvements for the next iteration are determined. The fifth section summarizes the previous sections, explains the contributions of the thesis, and discusses possible future work.
  • Öge
    Potential wind farm design of the Caspian sea shores of Azerbaijan
    (Graduate School, 2022-06-23) Isayev, Tural ; Beji, Serdar ; 508181223 ; Offshore Engineering
    Renewable energy sources include the sun, wind, water, the Earth's heat, and plants, all of which are perpetually renewed by nature. Renewable energy technologies convert these fuels into useable energy, such as electricity, heat, chemicals, or mechanical energy. Fossil fuels are now utilized to heat and power houses, as well as to fuel automobiles. Coal, oil, and natural gas are convenient for providing our energy demands, but there is a finite quantity of these fuels on the planet. We're consuming them at a far faster rate than they're being generated. They'll eventually run out. And, due to safety concerns and waste disposal issues, the US will phase down much of its nuclear power capacity by 2020. Meanwhile, the country's energy demands are predicted to increase by 33% during the next 20 years. Renewable energy may be able to fill the void. Renewable energy is better for the environment even if we had a limitless supply of fossil resources. Renewable energy systems are frequently referred to as "clean" or "green" since they create little, if any, pollutants. Renewable energy will also assist us in achieving energy security and independence. Replacing part of our petroleum with plant-based fuels, for example, may save money while also increasing our energy security. Renewable energy is abundant, and technology is always improving. Renewable energy may be used in a variety of ways. In our daily lives, the majority of us currently utilize renewable energy. The design of the wind farm has been researched in the fourth chapter. This section focuses on selecting the best site for the wind farm. The situation of the wind blowing around the Absheron area is described in general. The absheron region appears to be typically adequate in terms of wind speed when we look at the wind maps during the studies. In terms of depth, it appears that the region's depth ranges between 20 and 40 meters. On the other hand, the presence of onshore wind farms in the northern half of the Absheron peninsula makes this region more grid-connected. In terms of wind speed, the location in the southern portion of the Absheron peninsula where the wind speed of 7.69 m/sec was found to be the most favorable (A region). However, as previously noted, the sea section in the northern half of the Absheron peninsula is the best location for grid connection. Part B, in one of the zones with the highest wind speed closest to the land, has been judged to be the most suited location. The greatest water depth in this area is 20 meters, and the monopile foundations for the wind turbines to be erected are considered adequate. Furthermore, it has been found that ship traffic is not a barrier for this region, and as is well known, Azerbaijan has oil and natural gas deposits in the Caspian, and there is no pipeline running through this region, despite the threat of underwater pipes. The Vestas117-4.2 MW model was chosen as the wind turbine's model. Because the selected wind turbine's hub height is 91.5 meters, a reference wind speed of 50 meters (8.25 m/sec) was used, and the wind speed at 91.5 meters was found to be 8.7 m/sec. Furthermore, the annual energy production of a wind turbine was calculated based on its data to be 14.7 GWAC/year
  • Öge
    The use of hybrid energy storage systems in commercial vessels and potential contribution to emission reduction in Turkish straits
    (Graduate School, 2023) Ulutaş, Ferhat ; Güney Bilgin, Ceren ; 508191209 ; Offshore Engineering Programme
    In this thesis use of hybrid energy storage systems (HESS) in commercial ships's auxiliary power system (not for propulsion) was investigated in terms of emission reduction during maneuvering and strait passages. For the HESS proposed in this thesis, the appropriate battery group has been determined for a 10-year service period, taking into account the characteristics of the battery types to be used as well as the load characteristics of the ship. In the first part of the study a hypothetical study was carried out on a real commercial tanker vessel sailing in Turkey's inland waters and frequently using the Çanakkale and Istanbul straits. First of all, the actual fuel consumption data of the ship was analyzed and the emissions and fuel consumption during local maneuvers and channel navigation were evaluated on a 2-year basis. Afterwards, the same parameters were then evaluated for the case of having a hybrid energy storage system for the auxiliary power system on board. These analyses show that the use of hybrid auxiliary systems on commercial vessels leads to a reduction in local emissions. In the second part of the study, using the annual maritime traffic data of the Istanbul and Çanakkale straits, which have the highest maritime traffic in Turkey, the potential emission reductions in the straits were calculated if ships transiting these straits used a hybrid energy system instead of keeping two generators running to ensure the operational continuity of their auxiliary systems. In this context; The components of hybrid energy systems used on-board ships and their decisive criteria have been checked. Battery types which are used in Battery-Hybrid systems have been checked. Engineering and operational challenges such as power fluctuations which must be compensated, have been investigated.
  • Öge
    Comprehensive assessment of rov systems: An effective approach to analysis of ROV system mobilization risks
    (Graduate School, 2023-06-12) Asgarov, Gurban ; Menteş, Ayhan ; 508191238 ; Offshore Engineering
    Remote Operating Vehicles (ROVs) are sophisticated underwater robots that play a vital role in various industries such as deep-sea exploration, oil and gas operations, underwater construction, and scientific research. These ROV systems consist of several components, including the ROV itself, Launch and Recovery Systems (LARS), umbilical cables, tethers, and power generators. Due to their complexity, it is crucial to conduct a thorough risk analysis to identify and mitigate potential hazards associated with ROV operations. This study specifically focuses on the mobilization phase of ROV systems, which involves preparing and deploying the underwater robots. During mobilization, numerous risks can arise, including mechanical or technical failures during transportation, damage to the ROV or its components during handling, and delays or disruptions caused by adverse weather conditions or logistical issues. Safeguarding against these risks is paramount to ensure the safe and successful operation of ROVs. To assess the risks involved in the mobilization process, two hybrid approaches are employed in this study. Both methods utilize the Ordered Weighted Geometric Average (OWGA) for weight distribution in terms of Severity, Detection, and Occurrence. In addition, Multi-Objective Optimization on the Basis of Ratio Analysis (MOORA) and Multi-Objective Optimization on the Basis of Simple Ratio Analysis (MOOSRA) are utilized in calculating the Risk Priority Number (RPN). These approaches aim to provide a comprehensive evaluation of the risks associated with ROV mobilization, taking into account various factors and expert opinions. By utilizing these hybrid methodologies, operators and stakeholders can gain a better understanding of the potential risks involved and make informed decisions to mitigate them effectively. In conclusion, the analysis of risks in ROV systems, particularly during the mobilization phase, is crucial for ensuring safe and successful operations. By employing hybrid approaches and incorporating expert opinions, this study aims to enhance risk assessment capabilities and facilitate the implementation of effective risk mitigation strategies in the field of underwater robotics.
  • Öge
    Numerical modelling of waves and current acting on piles
    (Graduate School, 2023-06-21) Bal, Kemal ; Bural Bayraktar, Deniz ; 508201217 ; Offshore Engineering
    Calculating the applied forces of pile structures exposed to waves and currents is an important issue in the offshore industry. Because these constructs are costly, they must be carefully analyzed before evaluating all results. For designers, physical models can be cost and time constraining while helping them optimize their designs. Therefore, the use of numerical models provides a significant advantage. While numerical models offer flexibility in the design of complex structures, their accuracy must be compatible with physical experiments. In this study, the effects of a pile on a flat ground subjected to waves were numerically modeled. These numerical models were solved using the open-source computational fluid dynamics code called REEF3D. In addition, a mesh-convergence study was performed to determine the optimal mesh size. Numerical models of wave and current study samples were constructed using the optimal mesh size and the results were compared with experimental data and analytical results. It was observed that the numerical model was compatible with the experimental results in pile structures affected by waves and currents. First, two test scenarios were created for validation. In the first of these scenarios, only current effects were observed. These current effects were compared with the results of previous physical experiments. Some observation points were used in this comparison. These observation points were placed at certain distances from the single pile perpendicular to the base. The velocity information obtained from the observation points was compared with the numerical model results modeled with REEF3D and velocity profiles were obtained. These velocity profiles were found to be compatible with the results of the physical experiment and the numerical model. In the second verification scenario, only wave effects were observed. Wave forces acting on a fixed diameter cylinder were investigated. Numerical models were established and the results were obtained. These results were compared with the Morison equation results and the results were found to be consistent. After both verification scenarios were made, it was revealed that both wave and current forces can be modeled correctly with the REEF3D program. After this step, the forces acting on four different pile types in eight different scenarios were examined. To understand the diffraction effects, half of the eight scenarios were constructed with parameters where diffraction effects were considered important. At the beginning of these parameters is the change of the pile diameter. In the first of four different piles in eight scenarios, a pile diameter with a constant diameter and such that diffraction effects can be ignored was chosen. A new pile of this diameter was then created to create a cone of appropriate proportions. Wave and current forces acting on this new cone-shaped pile were calculated. The forces acting on both the fixed diameter pile and the cone shaped pile were compared with the results of the Morison and Beji equations and it was seen that reasonable results were obtained. On the other hand, pile scenarios with relatively larger diameters were created and fixed diameter and cone-shaped piles were remodeled in these pile scenarios. Evaluation of all results was re-evaluated and reasonable results were found. A separate mesh-convergence study was performed for all cases. For the mesh convergence study, a coarse mesh size was chosen and gradually reduced. It was desired to see whether it converged to such a value or not. The mesh created by the meshconvergence study were optimized and it was predicted that it could yield reasonable results. At the end of the studies, the compared results were presented both in tabular form and graphically. These results, obtained thanks to open-source tools, showed that we can produce solutions to engineering problems with REEF3D. In the final case, the forces generated by different waves and currents acting on the pile placed on a flat base were analyzed. Thanks to this study, wave or current forces acting on the piles were calculated, and further studies revealed that both wave and current forces could be calculated by computational fluid dynamics method. The use of numerical models has been a turning point in the analysis of pile structures exposed to waves and currents. Due to the limitations and costs of traditional physical experiments, the flexibility and cost-effectiveness of numerical models provide a great advantage. Open-source computational fluid dynamics codes such as REEF3D allow engineers to further examine the behavior of pile structures. This study demonstrates the potential of REEF3D for the analysis of pile structures exposed to waves and currents. It has been shown that the forces acting on the pile structures can be accurately calculated using numerical models. This helps designers make better decisions about the safety and durability of piles. In addition, the validation scenarios and analyzes performed in the study showed that the numerical models are compatible with the experimental data and analytical results. This supports the reliability and accuracy of the numerical models. The results of the study emphasize that numerical models are an important tool in the design of pile structures exposed to waves and currents. Using these models, designers can better understand, optimize, and safely design the behavior of piles. In the future, more advanced numerical models are expected to be developed and used for the analysis of more complex pile structures and different environmental conditions. Moreover, it will be possible to obtain more comprehensive and accurate results by integrating different open-source tools and computational methods.
  • Öge
    Landing dampers for aircraft carrier decks
    (Graduate School, 2024-07-09) Pekdemir, Mustafa Enes ; Köroğlu, Serdar Aytekin ; 508211213 ; Offshore Engineering
    Shock absorbers are integral components in mitigating landing events, especially within the context of aircraft carrier landing gear design, where the formidable impact forces of horizontal or vertical landings are prevalent. Typically crafted from elastomeric materials such as pads or cables, these shock absorbers are meticulously engineered to absorb and dissipate energy upon the abrupt contact of an aircraft with the carrier deck, thus effectively reducing the force of impact. The primary objective of this study is to undertake a comprehensive analysis and evaluation of the performance exhibited by landing dampers employed during landing operations on aircraft carrier decks. This endeavour involves a multifaceted approach that encompasses various methodologies including data analysis, numerical modelling, simulations, and real-world testing. Through this concerted effort, the efficacy of these dampers is being rigorously assessed to provide a holistic understanding of their functionality. Moreover, this study endeavours to embark on the development of shock absorber designs tailored specifically for ship decks, based on the insights garnered from the aforementioned analyses. These designs are then subjected to dynamic analysis to ascertain their structural integrity and operational efficiency under realistic conditions. By leveraging advanced analytical techniques, this phase aims to optimize shock absorber designs, thereby enhancing their performance and reliability during landing operations on aircraft carrier decks. Furthermore, a comparative analysis is being conducted to juxtapose the functionality of shock-absorbing deck designs against their non-shock-absorbing counterparts. This comparative study seeks to elucidate the distinct advantages and efficacy offered by the integration of landing dampers into aircraft carrier deck configurations. By highlighting the inherent benefits of shock-absorbing deck designs, this analysis underscores their pivotal role in bolstering the safety and operational efficiency of aircraft carrier landings. In conclusion, the findings of this study are poised to make significant contributions to the field of maritime engineering by enhancing our understanding of landing dampers and their impact mitigation capabilities. By optimizing shock absorber designs and elucidating their advantages, this research endeavour not only augments the safety and operational efficiency of aircraft carrier landings but also furnishes invaluable insights for the optimization of shock absorber designs in diverse maritime environments.