LEE- Gemi ve Deniz Teknolojisi Mühendisliği-Yüksek Lisans
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ÖgeTicari gemilerin sualtı gürültülerinin deniz yaşamına etkilerinin azaltılması yöntemleri, MEPC.1/CIRC 906 kılavuzun incelenmesi(Lisansüstü Eğitim Enstitüsü, 2024-12-26)Sualtı akustiği ile ilgili ilk deney, 1826 yılında İsviçreli fizikçi Jean-Daniel Colladon (1802–1893) ve asistanı Jacques Charles-Francois Sturm (1803–1855) tarafından gerçekleştirilmiştir. Bu deney, sesin suda yayılma hızının havadaki yayılma hızından daha hızlı olduğunu göstermiştir. Deney sırasında iki tekne arasındaki mesafe 10 mil (16 km) olarak belirlenmiş ve iletişim, bir su çanı ile sağlanmıştır. Colladon ve Sturm, deneyde sualtındaki ses dalgalarını gözlemlemek ve bu dalgaların yayılma hızını ölçmek için hem teknik bir yaklaşım hem de yaratıcı bir düşünce yöntemi kullanmıştır. Bu çalışmada, ses dalgalarının su ortamında ne kadar etkili bir şekilde ilerlediği ve havadaki hızlarına oranla çok daha hızlı bir şekilde hareket ettiği kesinleşmiştir. Ayrıca, deneylerden elde edilen ses hızı verileri modern teknolojiyle yapılan ölçümlerle kıyaslandığında oldukça yakın sonuçlar vermiştir. Bu buluş, sualtı akustiği alanındaki bilimsel çalışmaların temelini oluşturarak, gelecekteki pek çok akustik ve deniz bilimi araştırmasına yön vermiştir. Colladon ve Sturm'un bu öncü çabası, hem sualtı iletişim sistemlerinin gelişimine hem de denizcilik alanında yeni teknolojilerin doğmasına katkı sağlamıştır. 20. yüzyılın başlarına gelindiğinde, denizaltıların ve deniz savaşlarının yaygınlaşmasıyla birlikte sualtı akustiğinin önemi büyük ölçüde artmıştır. Bu döneme kadar sualtı akustiği yalnızca basit eko konumlama ve derinlik tespiti ile sınırlı bir alandı. Ancak 20. yüzyılın başlarındaki teknolojik gelişmeler ve özellikle denizaltıların stratejik öneminin artması, bu alandaki çalışmaları hızlandırmıştır. Deniz savaşlarında üstünlük sağlamak isteyen ülkeler, sualtı akustiği teknolojisine büyük yatırımlar yaparak, hem denizaltı tespit hem de iletişim sistemlerini geliştirmiştir. İlk etapta, denizaltıların diğer denizaltılardan ve su araçlarından gelen sesi algılayan pasif sonar sistemleri üzerine yoğunlaşılmıştır. Pasif sonarlar, herhangi bir sinyal yaymadan yalnızca çevredeki sesleri dinleyerek bilgi toplama prensibine dayanmaktadır ve bu sistemler sessiz operasyonların kritik olduğu durumlarda büyük avantaj sağlamıştır. Daha sonraki dönemde, aktif sonar sistemleri geliştirilmiştir. Bu sistemler, ses dalgalarını sualtında yayarak, bu dalgaların hedeflerden geri yansıyan yankılarını tespit etmek amacıyla kullanılmaktaydı. Aktif sonarların geliştirilmesiyle, yalnızca mevcut denizaltıları algılamakla kalınmamış, aynı zamanda sualtı haritalama ve keşif çalışmaları da hız kazanmıştır. İkinci Dünya Savaşı'nın sona ermesiyle birlikte, bu alanda elde edilen teknolojiler sismik araştırmalarda ve deniz biyolojisinde geniş kullanım alanı bulmuştur. Bu dönemde savaş sırasında geliştirilen sonar ve akustik cihazlar, bilimsel amaçlar için adapte edilmiştir. Sanayileşmenin ve deniz ticaretinin hızla artmasıyla birlikte deniz trafiğindeki yoğunluk önemli ölçüde artmış ve bu durum sualtı gürültü seviyelerinin daha detaylı bir şekilde incelenmesi ihtiyacını doğurmuştur. Artan deniz trafiği, özellikle ticari gemilerden kaynaklanan gürültünün deniz yaşamı üzerindeki etkilerini araştırma gerekliliğini artırmıştır. Bu bağlamda, Uluslararası Denizcilik Örgütü (IMO) bünyesinde faaliyet gösteren ve deniz temizliği ile ekosistemlerin korunması amacıyla kurulan Deniz Kirliliğini Önleme Komitesi (MEPC), bu alanda önemli adımlar atmıştır. Komite, 2014 yılında ticari gemilerden kaynaklanan sualtı gürültüsünün azaltılmasına yönelik bir kılavuz yayınlamıştır. Bu kılavuz, gürültü kaynaklarını ayrı ayrı değerlendirmiş, çözümleme metotlarına yer vermiş ve çözüm yöntemleri için detaylı bir uygulama matrisi eklemiştir. Söz konusu matriste, çözüm teknikleri kaynaklarına göre gruplandırılmış; tersaneler veya armatörlere getireceği finansal yükler detaylı olarak değerlendirilmiş; teknolojik olarak uygulanabilirlik puanlanmış ve çözüm yöntemlerinin hangi frekans aralıklarında etkili olduğu belirtilmiştir. Ayrıca, gürültü azaltım yöntemleri farklı kategorilere ayrılarak, bu yöntemlerin etkinliği ve uygulanabilirliği sınıflandırılmıştır. Bu kılavuz, yalnızca deniz yaşamının korunması için bir rehber niteliği taşımakla kalmamış, aynı zamanda sürdürülebilir denizcilik faaliyetleri için de önemli bir referans olmuştur. Tez çalışmamda ISO 17208-1 standardına uygun ölçüm metodolojisi incelenmiştir. Bu ölçüm standardındaki ölçümde kullanılacak ekipmanların (hidrofon, veri analizörü, uzaklık ölçüm aletleri) kapasite, ölçüm aralıkları, standart sapmaları, kalibrasyon ve doğrulama periyotları ve ölçüm belirsizlikleri standartta geçen metinler özenle incelenip özetlenmiştir. İlgili standartta tanımlanan test koşulları detaylı bir şekilde açıklanmış, hidrofonun bağlama yöntemleri ve test edilecek geminin yapacağı manevralar incelenmiştir. Ayrıca, bu ölçüm sonrası elde edilen verilerin işlenmesi sürecinde kullanılan arka plan seslerinin ölçüm verilerine dahil edilme formülleri ve verilerin güvenilir sonuçlara dönüştürülmesi için izlenen yöntemler çalışmamın önemli bir parçası olarak sunulmuştur. Gürültü kaynaklarının tanımlanması ve bu kaynaklarla ilgili özet bilgiler detaylı olarak verilmiş, farklı senaryolar için uygulanabilir çözüm yolları incelenmiştir. Bunun yanında, Türk gemi inşa sektörünün güncel durumu ve bu sektörde gelecekte yapılabilecek teknolojik atılımlar ele alınmıştır. Sektöre yönelik olarak geliştirilen çözüm önerileri tezin sonuç bölümünde detaylandırılmıştır.
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ÖgeThe effect of bilge keel on the roll motion of a naval destroyer(Graduate School, 2024-12-03)In this master's thesis, ship roll damping systems have been examined, and the effectiveness of bilge keel as a roll damping system has been parametrically evaluated using the DTMB 5415 high speed displacement hull form. Roll motions pose a range of problems that can adversely affect the performance of marine vessels. These motions can cause damage to the ship's cargo, decrease crew efficiency, and negatively impact weapon systems on warships. Additionally, roll motions can create issues during aircraft and helicopter landings and takeoffs on warships and reduce the accuracy of weapon systems. Systems used to control roll motions are generally categorized into two main types: active and passive roll damping systems. These systems aim to reduce roll motions through various methods. The roll damping measures discussed are as follows: Passive roll damping systems include bilge keels and passive roll reduction tanks. Bilge keels are a traditional, cost-effective method that effectively dampens roll motions. They are simple to manufacture and are often combined with active systems on warships. Passive roll reduction tanks, on the other hand, achieve roll damping by balancing the movement of liquids within the vessel. Active roll damping systems feature gyro stabilizers, active roll reduction tanks, fin stabilizers, and rudder-controlled stabilizers. Gyro stabilizers are highly effective at low speeds and during anchorage, as they operate within a fully enclosed box, protecting them from external damage. This design allows for safe navigation in shallow waters. Active roll reduction tanks actively balance the ship's motion, while fin stabilizers mitigate rolling caused by waves or external forces. These stabilizers use sensors and control systems to dynamically adjust their fins, ensuring effective roll damping. Fin stabilizers must remain submerged during ship inclination, be located in protected areas of the hull, and minimize water flow disturbance. To address collision risks, foldable fins have been developed, allowing retraction when not in use. Despite their high cost, fin stabilizers are highly efficient, particularly in challenging sea conditions, and are widely used on various vessels, including yachts, cruise ships, warships, and cargo ships. Additionally, they must be installed in a manner that does not disturb the water flow. Active fin stabilizer systems, being mounted on the exterior of the ship, pose a collision risk; thus, foldable fins have been developed. These foldable fins can be retracted into the vessel when not in use, thereby minimizing additional resistance to the ship. Fin stabilizers are particularly effective in challenging conditions such as head seas and cross seas and are considered the most efficient equipment for roll damping. Advanced fin stabilizers are now produced for a wide range of vessels, from yachts and cruise ships to warships and commercial cargo ships. Despite their high cost, these systems are preferred for their effective performance. Rudder roll stabilizers use the ship's rudder to balance roll motions. However, they are generally not effective at low speeds and while the ship is at anchor. Rudder-controlled roll stabilization systems are advantageous because they do not add extra weight or volume to the ship. The history of roll damping systems began with William Froude's free surface tanks and Frahm's U-type passive roll tanks. The use of bilge keels extends back to the early 20th century, with fin systems beginning to be employed in the 1930s. In the subsequent sections of the study, parametric analyses have been conducted using different bilge keel geometries on the 5415 model bare hull to investigate the effect of bilge keels on roll damping. Prior to these parametric analyses, a validation was performed by comparing experimental roll damping results of the 5415 model bare hull with results from AQWA© software. This comparison yielded highly favorable results. Ikeda's viscous roll damping method has been thoroughly examined to account for viscous effects in validation and parametric analyses. The Ikeda method has been used to detail and examine the critical roll damping method and calculation techniques. When viscous effects are incorporated into the AQWA© program, the roll values for the structure are found to be very close to the expected values by experiments. Following the completion of the validation work, parametric analyses were performed using AQWA© software with a total of six different bilge keels, utilizing the bilge keels of the DTMB 5415 model ship. In these parametric analyses, the angle, width, and length of the bilge keels were systematically varied, and the model ship was analyzed with these bilge keels at different speeds. The analyses concluded that examining parameters such as the width, length, and angle of the bilge keels individually would be insufficient; instead, all relevant parameters should be considered together in the analysis.
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ÖgeStandard shipyard format for repair budget calculations of vessels at dock and relationship between the work scope and the repair period(Graduate School, 2025-01-23)Shipyards are facilities where ships are built, repaired, and maintained. The reasons for repairs can be accidents or obligatory maintenance. Shipowners prefer shipyards that are near to the trading areas in order to avoid transportation costs. However, the selection of a shipyard can also be affected due to the quotes of faraway shipyards. It is well known that realistic repair budgets and repair timelines are considered as key elements in the selection of shipyards, but due to the inconsistencies in the repair reports, different formats, and lack of information, these budgets and timelines usually result in overruns and delays. After all, ship-owners try to maximize profit during a ship's life cycle, but repair processes in shipyards constitute one of the biggest costs and losses. The repair budgets of ships are prepared based on the developed repair reports by the ship's superintendent. These reports include details about works such as steel renewal, mechanical fixes, and docking activities. They can be used as a gross indication of the total repair cost. The estimates of the budget, however, depend on the repair period, dimensions of the ship, type, and tonnage, in addition to the superintendent report. However, due to the vagueness or incompleteness of the specifications, the precise pricing of repairs is by no means easy for the marketing departments of shipyards. Shipyards usually present their offers in their own formats and comparisons among several bids become difficult for the shipowners. The lack of a specification standard frequently leads to many of errors, ineffective communication, disputes and increased costs for shipowners. Ship repair periods are one of the most important parameters in a shipyard offer. Repair times vary depending on the work to be done on the ships and the shipyard's busyness. Explaining the relationship between repair work and repair times can help in making predictions about future ship repairs. Providing a correct repair time will not affect negatively the shipyard's future plans, will not increase the cost in the budget and will make the offer more attractive and realistic. A literature survey of various methods for ship repair budget estimation was carried to identify gaps in current techniques for budget estimation. Common factors for such techniques are that they require consistent information about the ship type, dimensions and type of repairs required. However, not enough research has been carried out in standardizing the specifications and procedures for repair and budgeting. Furthermore, most of the analysed approaches have a bias towards the shipowners or shipyards and thus, a major reason for that universally applicable solutions are difficult to develop. Serious challenges include the non-standard practices and unexpected repair requirements. Lack or inconsistency in the data within the repair reports leads to delay, disputes, and increased costs in the repair process. The inconsistency in bids due to different interpretations of the repair specification may lead to shipowners choosing inappropriate shipyards. Unexpected repair requirements discovered during the shipyard period result in increased costs and extended timelines of repairs. In addition, a uniform approach to the repair specifications is discussed. These standard specifications would enable shipyards to make precise bids supported by detailed and consistent repair lists, while shipowners could evaluate the bids equitably and effectively. Key components of repair specifications are the details of ships such as length, gross tonnage, thorough descriptions of repairs, time schedules, and accompanying technical drawings. They would allow shipyards to provide a more accurate estimation of the repair costs, and shipowners to evaluate the most adequate shipyard based on more accurate information from the bids, as well as ensuring that the extent of repair works is precisely defined, accurately priced, and consistently considered.
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ÖgeViv of a single cylinder and two cylinders in tandem arrangement: A comparative study of results and energy calculations for maritime renewable energy utilization(Graduate School, 2024-06-11)Renewable energy sources have become increasingly important today, especially when considering the various negative effects and harms caused by other types of energy. When we take the environmental and health impacts of energy sources like coal, gas, and oil into account, it becomes clear that renewable energy should be utilized more extensively in our lives. Some of the negative effects of energy sources other than renewable ones include air pollution, depletion of the ozone layer, reduction of natural greenery, and the proliferation of diseases like cancer among humans. These undesired impacts carry significant risks to both human and environmental health. Therefore, it is essential to understand the necessity of incorporating renewable energy into our lives as a substitute for other energy types. There are many sources available for renewable energy production. Among these, it is essential to highlight solar and water. Renewable energy sources that can be obtained from water include ocean thermal energy, osmotic power, underwater kite systems, tidal energy, and ocean current energy. Vortex-Induced Vibration (VIV) is a phenomenon that can be utilized to harness renewable energy using water as a source. VIV is caused by the formation of the vortices in the fluid flow. When the fluid flow passes the structure, it creates alternating areas of high and low pressure fields around the structure. These pressure differences lead to the generation of vortices, which are swirling regions of fluid motion. In other words, VIV is caused by flow separation from bluff bodies and leads to oscillations. VIV is a subset of Flow-induced motion (FIM). In VIV, the flow exerts a force on the object. The body will move with a frequency in relation to its natural frequency and eddy break frequency. This will lead to a high order nonlinear problem and make it harder to solve. Flow separations occur when a structure is not aligned with the hydrodynamics of the flow. Eddies are formed when the flow leaves the object and eventually creates force on it. When VIV occurs on a body in water, it is possible to implement a system that can convert the hydrokinetic energy in the water into mechanical energy. Useful energy extraction from flowing water is one of the hot topics of the academic literature today. Among the many devices that are developed towards this goal, VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) stands out. It is a converter that converts the ocean/river current energy to electricity. A VIVACE has the aim of maximizing VIV and converting its mechanical energy extracted from the moving fluid flow into electrical power. From the structural perspective, VIV is an unwanted phenomenon as it disturbs and causes damage to a structure. However, it can also prove beneficial by harnessing energy through the utilization of an oscillator system, converting the mechanical energy obtained from these oscillations into electricity, all without impeding its Flow Induced Oscillations (FIO). VIV can be excited in a wide range of Reynolds numbers. This means that by having a Reynolds number of Re>50, this system can be utilized for energy and power generation across a broad range of flow regimes. Although lab-scale prototypes of VIVACE systems can generally reach the maximum Reynolds number of 1.35×〖10〗^5, full-scale VIVACE systems have the potential to reach 〖10〗^7, proving the scalability of the device. VIV can also be identified as a synchronization between vortex shedding and cylinder oscillations. The main aim of VIVACE converter is to enhance the vortex shedding rather than spoiling and maximize under significant damping rather than suppressing VIV's. This converter can extract energy from currents of velocities 0.5
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ÖgeTechno-economic investigation of alternative propulsion systems for fishing vessels(Graduate School, 2024-09-17)Main objective of this thesis is to analyze the techno-economic aspects of the propulsion chain and power supply units in fisheries. The global agricultural sector is vital for supporting the food needs of the growing population, contributing to national economies, and creating new job opportunities. Aquaculture forms the marine interest of this system. Fishing, a significant component of marine and ocean aquaculture, not only provides food but also supports economic development and consumer welfare in many countries. However, overfishing and technological advancements have led to decline in fish populations over time. This has made the implementation of sustainable management systems imperative. This study provides information on agricultural activities, fish production processes, and fish farming and fishing in Turkey. As it is known, the Republic of Turkey is surrounded by seas on three sides. This situation highlights the importance of aquaculture and fishing for our country. The study identifies fundamental challenges such as environmental pollution, regulatory issues, and technological inadequacies resulting from this fishing and aquaculture. Main focus of the thesis is the analysis of power systems used in fishing vessels, including diesel, hybrid, LNG (Liquefied Natural Gas), and dual-fuel systems. The research examines the detailed operation schedules of predetermined vessels, the devices used in operations, the annual fuel energy consumption of alternative fuel systems, lubrication oil usage, initial investment costs, and long-term operational costs. The study also provides a comprehensive cost-benefit analysis over a 20-year period by evaluating the life cycle costs of these propulsion systems. The cost efficiency and effectiveness of the most commonly used diesel systems are examined. Additionally, the potential of hybrid systems, which combine diesel and electric power, to reduce fuel consumption and emissions is evaluated. The LNG systems, an emerging and promising alternative fuel, are assessed for their environmental benefits and economic feasibility. The comparative analysis of these systems aims to identify the most sustainable and cost-effective options for the fishing industry. Techno-economic indicators are used to evaluate how the introduction of different fuel types will impact the fishing community. The study examines factors such as employment, income levels, and the overall economic well-being of fishermen to understand the socio-economic changes brought by these new systems. The importance of integrating techno-economic indicators with biological indicators to ensure the sustainability of fishery resources is emphasized. The analyses show that diesel systems still maintain their validity for the fishing industry. However, it is observed that hybrid, LNG, and dual-fuel propulsion systems have minimal environmental impact when examined in the long term. It is found that this minimal environmental impact can also provide economic benefits in the long term. This situation underscores the need for governments, fishing fleet owners, and fishing vessel operators to work together to promote more sustainable and technologically supported measures for the future of fishing. In conclusion, this thesis also provides some valuable insights for stakeholders in the fishing industry, including boat owners, fishermen, and policy-makers, to make informed decisions that balance economic efficiency with environmental sustainability. The recommendations aim to promote the adoption of cleaner and more efficient fuel technologies, ensuring the long-term sustainability of the fishing industry and the preservation of marine resources.