Victor Bolbot | National Technical University of Athens (original) (raw)
Papers by Victor Bolbot
Journal of Navigation
The Autonomous Navigation System (ANS) constitutes a critical key enabling technology required fo... more The Autonomous Navigation System (ANS) constitutes a critical key enabling technology required for operating Maritime Autonomous Surface Ships (MASS). To assure the safety of MASS operations, the effective identification of potential objects and target ships interacting with the own MASS is quintessential. This study proposes a systematic method to identify the items interacting with the own MASS. This method is based on a similar approach previously employed for the encountering items’ identification in robotics, which is customised herein for the MASS needs. The developed method is applied to a short-sea shipping MASS. The environmental features, agents and objects related to her navigation are identified and ranked based on the frequency of encounter and the potential collision consequences. The results demonstrate the ability of the method to identify additional items in comparison to Automatic Identification System based data. The interactions with the small ships are considere...
International Journal of Naval Architecture and Ocean Engineering
1st International Conference on the Stability and Safety of Ships and Ocean Vehicles, Jun 7, 2021
The maritime industry has been progressing towards autonomous shipping with a main barrier and sc... more The maritime industry has been progressing towards autonomous shipping with a main barrier and scepticism being on the safety assurance of the next-generation autonomous ships. This study aims to perform a safety analysis of the autonomous navigation of a Short Sea Shipping vessel. A conceptual system for the investigated of the system is proposed as reference, and input data for the Mean Time Between Failure of the most critical components are derived from the pertinent literature. Fault Tree Analysis is employed to calculate various metrics including the probability of failure, frequency of failure, and unavailability of the autonomous navigation function as the top event. This study results identified the critical components that contribute to the failure of the autonomous navigation function in next-generation unmanned MASS
1st International Conference on the Stability and Safety of Ships and Ocean Vehicles, Jun 11, 2021
The Marine Autonomous Surface Ships (MASS) constitute a novel type of systems, which require nove... more The Marine Autonomous Surface Ships (MASS) constitute a novel type of systems, which require novel methods for their design and safety assurance. The collision avoidance system is considered one of the most critical systems for MASS. This study aims at developing a process for generating and selecting ship encounter scenarios to test the collision avoidance system in a virtual environment. The proposed process employs sampling techniques for generating encounter scenarios, deterministic criteria for identifying the hazardous scenarios, risk metrics estimation for the classification of the encounter situations, as well as clustering techniques for further downsizing of the scenarios number. This process is applied to a small short-shipping vessel thus demonstrating its applicability
Maritime autonomous surface ships provide new capabilities for transport systems design, and by t... more Maritime autonomous surface ships provide new capabilities for transport systems design, and by that the potential to dramatically change ship logistics. Advantages of autonomous ships include operational flexibility with more and smaller ships, combined with new ship hull and superstructure designs, allowing more cargo to be transported at lower cost and reduced emissions. It is also easier to operate smaller ships with alternative energy sources such as batteries, and by that further reducing the emissions. However, the investment cost of an autonomous ship system is perceived to be higher compared with conventional ships. Combined with limited operational experience, this creates a challenging threshold for launching new projects.
Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability, 2021
Effectively addressing safety, security and cyber-security challenges is quintessential for progr... more Effectively addressing safety, security and cyber-security challenges is quintessential for progressing the development of next generation maritime autonomous shipping. This study aims at developing a novel hybrid, semi-structured process for the hazardous scenarios identification and ranking. This method integrates the operational and functional hazard identification approaches, whilst considering the safety, security and cybersecurity hazards. This method is applied to comprehensively assess the safety of an autonomous inland waterways ship at a preliminary design phase. The hazardous scenarios are identified and ranked by a number of experts participating in a series of sessions. The identified hazards risk is estimated considering the frequency and severity indices, whereas their uncertainty is estimated by employing the standard deviations in these two indices among the experts ranking results. Epistemic uncertainty is also considered during ranking. Risk control measures are p...
Every shipping company has a goal to reduce operational costs and increase income. One possible w... more Every shipping company has a goal to reduce operational costs and increase income. One possible way to achieve that is by optimizing ship's hull in respect to calm water resistance. However, because ships seldom travel at still water conditions, it is important also to introduce the effect of the added resistance in waves. For large ships, added resistance in waves is mainly the result of wave diffraction around the ship while the added resistance due to motions has a small contribution. The available theoretical methods at the moment find it hard to evaluate accurately the diffraction component of added resistance in short waves. This makes necessary the use of semi-empirical approach or CFD methods. Added resistance is also important for minimization of the Energy Efficiency Design Index (EEDI). Added resistance affects the selection of suitable Sea Margin and fw correction factor, which accounts for the decrease of speed in representative sea conditions. A reduction in added resistance will affect positively the EEDI. The development of computers during last century allowed the use of parametric models created in CAD/CAE systems for representation of hulls forms. New optimization solution techniques such as Sobol functions and genetic algorithms set up the necessary background for effective and quick optimization. All of these are present in CAESES/Friendship-Framework. In this diploma thesis, the bow of a large tanker (KVLCC2) is optimized in terms of the added resistance in waves using CAESES/Friendship-Framework for creation of parametric model and optimization. Ship's bow is also optimized for total resistance, using Holtrop-Mennen method for estimation of calm water resistance. In the last stage, ship's bow is optimized for EEDI. The resulted maximum continuous rating of ship's main engine is compared with the minimum required power in adverse conditions.
Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment, 2022
The liquified natural gas (LNG) is currently considered an attractive marine fuel in the short- t... more The liquified natural gas (LNG) is currently considered an attractive marine fuel in the short- to medium-terms that can lead to the reduction of the shipping industry carbon emissions. LNG fuelled ocean-going ships have been designed by employing either low-pressure or high-pressure fuel systems. This study aims at enhancing the safety of a high-pressure fuel gas supply system (FGSS) designed for ocean-going LNG fuelled vessels. A model-based safety analysis is performed by employing the MADe™ software. The functional model of the baseline design of the investigated system is developed and subsequently employed to carry out the Failure Modes, Effects and Criticality Analysis (FMECA), as well as the quantitative Fault Tree Analysis (FTA). FMECA provided the risk priority number (RPN) for the identified system failure scenarios, the analysis of which leads to the identification of the FGSS critical components. The FTA results, which include the probabilities of the selected top event...
Wind Energy Science, 2021
Diesel-Electric Propulsion (DEP) has been widely used for propulsion of LNG carriers, icebreakers... more Diesel-Electric Propulsion (DEP) has been widely used for propulsion of LNG carriers, icebreakers, drilling units, warships and cruise ships. It is important that every blackout is prevented, especially on cruise ships, considering the possible consequences of such an event. In this work, hazard analysis of a simplified DEP system of a cruise ship is implemented to identify the hazardous scenarios leading to a blackout. This is achieved by combining System-Theoretic Process Analysis (STPA) and Event Tree Analysis (ETA). The STPA is used to identify the hazards and the possible control actions leading to hazards along with their causal factors, whilst the ETA is used to determine the propagation of hazards into the other hazards or accident. Next, the results of STPA and ETA are mapped into a Fault Tree for better representation of results. In this way, the relationship between accident, hazards and unsafe control actions is explicitly described and a more comprehensive picture of th...
The stringent regulatory framework for both emissions and safety as well as the market pressure t... more The stringent regulatory framework for both emissions and safety as well as the market pressure to reduce the operational costs led the cruise ship industry to pursue alternative solutions. In this respect, multi-objective optimisation methods can be employed for decision-making for identifying optimal solutions with improved efficiency, lower environmental footprint, lifecycle cost as well as a safety level during the ship design phase. In this study, the optimal power plant solutions for an existing cruise ship are compared in terms of their Probability of Blackout (PoB). For this purpose, a novel power plant bi-objective optimisation method has been used whilst considering an actual cruise ship operational profile, a number of design parameters and alternative configurations. Then a Combinatorial Approach for Safety Assessment (CASA) that includes System-Theoretic Process Analysis, Event Sequence Identification and Fault Tree Analysis whilst taking into account a number of design...
New developments in maritime industry include the design and operation of autonomous ships. The A... more New developments in maritime industry include the design and operation of autonomous ships. The AUTOSHIP project is one initiative promoting the use of autonomous ships in European waters focusing on two specific use cases, a Short Sea Shipping (SSS) cargo vessel and an Inland Waterways (IWW) barge. The AUTOSHIP objectives include thorough regulatory, societal, financial, safety and security analyses for the two investigated use cases as well as the development of a novel framework and methods for the design of autonomous vessels. This objective is achieved with the support of a number of activities, including supply chain, regulatory, risk and gaps analyses. Some results and findings from these activities are presented in this paper. The results demonstrate that the supply chain analysis is important to understand the complex relationships between different partners and phases for the effective design of maritime autonomous systems. Furthermore, a number of regulatory gaps needs to...
Journal of Marine Science and Engineering, 2021
Recent regulatory requirements for shipping emissions control have led to the adoption of Liquefi... more Recent regulatory requirements for shipping emissions control have led to the adoption of Liquefied Natural Gas (LNG) as a marine fuel and the design of LNG-fuelled vessels. Considering the potential safety implications due to system failure/unavailability, this study aims at the safety analysis of a low-pressure LNG fuel feeding system using a novel model-based methodology. The proposed methodology is based on the functional system modelling, leading to the failure diagrams development, and combines the use of Failure Modes, Effects, and Criticality Analysis (FMECA) and Fault Tree Analysis (FTA), which are performed in MADe™ and PTC Windchill software environments. The FMECA results are employed to identify the investigated system critical components and failures as well as specifying the top events for the subsequently performed FTA, which evaluates the top events failure rates. The system critical components identification leads to the system design modification targeting reduced...
Safety, 2021
Diesel–Electric Propulsion (DEP) has been widely used for the propulsion of various ship types in... more Diesel–Electric Propulsion (DEP) has been widely used for the propulsion of various ship types including cruise ships. Considering the potential consequences of blackouts, especially on cruise ships, it is essential to design and operate the ships’ power plants for avoiding and preventing such events. This study aims at implementing a comprehensive safety analysis for a cruise ship Diesel–Electric Propulsion (DEP) plant focusing on blackout events. The Combinatorial Approach to Safety Analysis (CASA) method is used to develop Fault Trees considering the blackout as the top event, and subsequently estimate the blackout frequency as well as implement importance analysis. The derived results demonstrate that the overall blackout frequency is close to corresponding values reported in the pertinent literature as well as estimations based on available accident investigations. This study deduces that the blackout frequency depends on the number of operating Diesel Generator (DG) sets, the ...
Energies, 2021
Stringent environmental regulations and efforts to improve the shipping operations sustainability... more Stringent environmental regulations and efforts to improve the shipping operations sustainability have resulted in designing and employing more complex configurations for the ship power plants systems and the implementation of digitalised functionalities. Due to these systems complexity, critical situations arising from the components and subsystem failures, which may lead to accidents, require timely detection and mitigation. This study aims at enhancing the safety of ship complex systems and their operation by developing the concept of an integrated monitoring safety system that employs existing safety models and data fusion from shipboard sensors. Detailed Fault Trees that model the blackout top event, representing the sailing modes of a cruise ship and the operating modes of its plant, are employed. Shipboard sensors’ measurements acquired by the cruise ship alarm and monitoring system are integrated with these Fault Trees to account for the acquired shipboard information on the...
Proceedings of the International Seminar on Safety and Security of Autonomous Vessels (ISSAV) and European STAMP Workshop and Conference (ESWC) 2019, 2020
The adage "prevention is better than cure" is at the heart of safety principles. However, effecti... more The adage "prevention is better than cure" is at the heart of safety principles. However, effective accident prevention is challenging in complex, highly automated systems such as modern DP-driven vessels, which are supposed to safely transfer technicians in often unfavourable environmental conditions. FMEA analysis, which is required for DP-driven vessels, is helpful to build-in a necessary level of redundancy and thereby mitigate consequences of failures, but not particularly helpful to inform preventive measures, not least against functional glitches in controlling software. In this paper we develop a set of functional safety requirements which are aimed at prevention of causal factors behind drift-off, drive-off and other hazardous scenarios. For this purpose, we use a systemic hazard analysis by STPA, which delivers both failure and interaction-based (reliable-but-unsafe) scenarios. The functional requirements cover both design and operational (human element related) requirements, which are then ranked based on our proposed heuristic. The ranking is not predicated on statistics or expert option but instead it is proportional to the number of hazardous scenarios a requirement protects against, hence indicating the relative importance of the requirement. The paper also summarises the suggested areas of safety improvement for DP-driven vessels.
Journal of Navigation
The Autonomous Navigation System (ANS) constitutes a critical key enabling technology required fo... more The Autonomous Navigation System (ANS) constitutes a critical key enabling technology required for operating Maritime Autonomous Surface Ships (MASS). To assure the safety of MASS operations, the effective identification of potential objects and target ships interacting with the own MASS is quintessential. This study proposes a systematic method to identify the items interacting with the own MASS. This method is based on a similar approach previously employed for the encountering items’ identification in robotics, which is customised herein for the MASS needs. The developed method is applied to a short-sea shipping MASS. The environmental features, agents and objects related to her navigation are identified and ranked based on the frequency of encounter and the potential collision consequences. The results demonstrate the ability of the method to identify additional items in comparison to Automatic Identification System based data. The interactions with the small ships are considere...
International Journal of Naval Architecture and Ocean Engineering
1st International Conference on the Stability and Safety of Ships and Ocean Vehicles, Jun 7, 2021
The maritime industry has been progressing towards autonomous shipping with a main barrier and sc... more The maritime industry has been progressing towards autonomous shipping with a main barrier and scepticism being on the safety assurance of the next-generation autonomous ships. This study aims to perform a safety analysis of the autonomous navigation of a Short Sea Shipping vessel. A conceptual system for the investigated of the system is proposed as reference, and input data for the Mean Time Between Failure of the most critical components are derived from the pertinent literature. Fault Tree Analysis is employed to calculate various metrics including the probability of failure, frequency of failure, and unavailability of the autonomous navigation function as the top event. This study results identified the critical components that contribute to the failure of the autonomous navigation function in next-generation unmanned MASS
1st International Conference on the Stability and Safety of Ships and Ocean Vehicles, Jun 11, 2021
The Marine Autonomous Surface Ships (MASS) constitute a novel type of systems, which require nove... more The Marine Autonomous Surface Ships (MASS) constitute a novel type of systems, which require novel methods for their design and safety assurance. The collision avoidance system is considered one of the most critical systems for MASS. This study aims at developing a process for generating and selecting ship encounter scenarios to test the collision avoidance system in a virtual environment. The proposed process employs sampling techniques for generating encounter scenarios, deterministic criteria for identifying the hazardous scenarios, risk metrics estimation for the classification of the encounter situations, as well as clustering techniques for further downsizing of the scenarios number. This process is applied to a small short-shipping vessel thus demonstrating its applicability
Maritime autonomous surface ships provide new capabilities for transport systems design, and by t... more Maritime autonomous surface ships provide new capabilities for transport systems design, and by that the potential to dramatically change ship logistics. Advantages of autonomous ships include operational flexibility with more and smaller ships, combined with new ship hull and superstructure designs, allowing more cargo to be transported at lower cost and reduced emissions. It is also easier to operate smaller ships with alternative energy sources such as batteries, and by that further reducing the emissions. However, the investment cost of an autonomous ship system is perceived to be higher compared with conventional ships. Combined with limited operational experience, this creates a challenging threshold for launching new projects.
Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability, 2021
Effectively addressing safety, security and cyber-security challenges is quintessential for progr... more Effectively addressing safety, security and cyber-security challenges is quintessential for progressing the development of next generation maritime autonomous shipping. This study aims at developing a novel hybrid, semi-structured process for the hazardous scenarios identification and ranking. This method integrates the operational and functional hazard identification approaches, whilst considering the safety, security and cybersecurity hazards. This method is applied to comprehensively assess the safety of an autonomous inland waterways ship at a preliminary design phase. The hazardous scenarios are identified and ranked by a number of experts participating in a series of sessions. The identified hazards risk is estimated considering the frequency and severity indices, whereas their uncertainty is estimated by employing the standard deviations in these two indices among the experts ranking results. Epistemic uncertainty is also considered during ranking. Risk control measures are p...
Every shipping company has a goal to reduce operational costs and increase income. One possible w... more Every shipping company has a goal to reduce operational costs and increase income. One possible way to achieve that is by optimizing ship's hull in respect to calm water resistance. However, because ships seldom travel at still water conditions, it is important also to introduce the effect of the added resistance in waves. For large ships, added resistance in waves is mainly the result of wave diffraction around the ship while the added resistance due to motions has a small contribution. The available theoretical methods at the moment find it hard to evaluate accurately the diffraction component of added resistance in short waves. This makes necessary the use of semi-empirical approach or CFD methods. Added resistance is also important for minimization of the Energy Efficiency Design Index (EEDI). Added resistance affects the selection of suitable Sea Margin and fw correction factor, which accounts for the decrease of speed in representative sea conditions. A reduction in added resistance will affect positively the EEDI. The development of computers during last century allowed the use of parametric models created in CAD/CAE systems for representation of hulls forms. New optimization solution techniques such as Sobol functions and genetic algorithms set up the necessary background for effective and quick optimization. All of these are present in CAESES/Friendship-Framework. In this diploma thesis, the bow of a large tanker (KVLCC2) is optimized in terms of the added resistance in waves using CAESES/Friendship-Framework for creation of parametric model and optimization. Ship's bow is also optimized for total resistance, using Holtrop-Mennen method for estimation of calm water resistance. In the last stage, ship's bow is optimized for EEDI. The resulted maximum continuous rating of ship's main engine is compared with the minimum required power in adverse conditions.
Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment, 2022
The liquified natural gas (LNG) is currently considered an attractive marine fuel in the short- t... more The liquified natural gas (LNG) is currently considered an attractive marine fuel in the short- to medium-terms that can lead to the reduction of the shipping industry carbon emissions. LNG fuelled ocean-going ships have been designed by employing either low-pressure or high-pressure fuel systems. This study aims at enhancing the safety of a high-pressure fuel gas supply system (FGSS) designed for ocean-going LNG fuelled vessels. A model-based safety analysis is performed by employing the MADe™ software. The functional model of the baseline design of the investigated system is developed and subsequently employed to carry out the Failure Modes, Effects and Criticality Analysis (FMECA), as well as the quantitative Fault Tree Analysis (FTA). FMECA provided the risk priority number (RPN) for the identified system failure scenarios, the analysis of which leads to the identification of the FGSS critical components. The FTA results, which include the probabilities of the selected top event...
Wind Energy Science, 2021
Diesel-Electric Propulsion (DEP) has been widely used for propulsion of LNG carriers, icebreakers... more Diesel-Electric Propulsion (DEP) has been widely used for propulsion of LNG carriers, icebreakers, drilling units, warships and cruise ships. It is important that every blackout is prevented, especially on cruise ships, considering the possible consequences of such an event. In this work, hazard analysis of a simplified DEP system of a cruise ship is implemented to identify the hazardous scenarios leading to a blackout. This is achieved by combining System-Theoretic Process Analysis (STPA) and Event Tree Analysis (ETA). The STPA is used to identify the hazards and the possible control actions leading to hazards along with their causal factors, whilst the ETA is used to determine the propagation of hazards into the other hazards or accident. Next, the results of STPA and ETA are mapped into a Fault Tree for better representation of results. In this way, the relationship between accident, hazards and unsafe control actions is explicitly described and a more comprehensive picture of th...
The stringent regulatory framework for both emissions and safety as well as the market pressure t... more The stringent regulatory framework for both emissions and safety as well as the market pressure to reduce the operational costs led the cruise ship industry to pursue alternative solutions. In this respect, multi-objective optimisation methods can be employed for decision-making for identifying optimal solutions with improved efficiency, lower environmental footprint, lifecycle cost as well as a safety level during the ship design phase. In this study, the optimal power plant solutions for an existing cruise ship are compared in terms of their Probability of Blackout (PoB). For this purpose, a novel power plant bi-objective optimisation method has been used whilst considering an actual cruise ship operational profile, a number of design parameters and alternative configurations. Then a Combinatorial Approach for Safety Assessment (CASA) that includes System-Theoretic Process Analysis, Event Sequence Identification and Fault Tree Analysis whilst taking into account a number of design...
New developments in maritime industry include the design and operation of autonomous ships. The A... more New developments in maritime industry include the design and operation of autonomous ships. The AUTOSHIP project is one initiative promoting the use of autonomous ships in European waters focusing on two specific use cases, a Short Sea Shipping (SSS) cargo vessel and an Inland Waterways (IWW) barge. The AUTOSHIP objectives include thorough regulatory, societal, financial, safety and security analyses for the two investigated use cases as well as the development of a novel framework and methods for the design of autonomous vessels. This objective is achieved with the support of a number of activities, including supply chain, regulatory, risk and gaps analyses. Some results and findings from these activities are presented in this paper. The results demonstrate that the supply chain analysis is important to understand the complex relationships between different partners and phases for the effective design of maritime autonomous systems. Furthermore, a number of regulatory gaps needs to...
Journal of Marine Science and Engineering, 2021
Recent regulatory requirements for shipping emissions control have led to the adoption of Liquefi... more Recent regulatory requirements for shipping emissions control have led to the adoption of Liquefied Natural Gas (LNG) as a marine fuel and the design of LNG-fuelled vessels. Considering the potential safety implications due to system failure/unavailability, this study aims at the safety analysis of a low-pressure LNG fuel feeding system using a novel model-based methodology. The proposed methodology is based on the functional system modelling, leading to the failure diagrams development, and combines the use of Failure Modes, Effects, and Criticality Analysis (FMECA) and Fault Tree Analysis (FTA), which are performed in MADe™ and PTC Windchill software environments. The FMECA results are employed to identify the investigated system critical components and failures as well as specifying the top events for the subsequently performed FTA, which evaluates the top events failure rates. The system critical components identification leads to the system design modification targeting reduced...
Safety, 2021
Diesel–Electric Propulsion (DEP) has been widely used for the propulsion of various ship types in... more Diesel–Electric Propulsion (DEP) has been widely used for the propulsion of various ship types including cruise ships. Considering the potential consequences of blackouts, especially on cruise ships, it is essential to design and operate the ships’ power plants for avoiding and preventing such events. This study aims at implementing a comprehensive safety analysis for a cruise ship Diesel–Electric Propulsion (DEP) plant focusing on blackout events. The Combinatorial Approach to Safety Analysis (CASA) method is used to develop Fault Trees considering the blackout as the top event, and subsequently estimate the blackout frequency as well as implement importance analysis. The derived results demonstrate that the overall blackout frequency is close to corresponding values reported in the pertinent literature as well as estimations based on available accident investigations. This study deduces that the blackout frequency depends on the number of operating Diesel Generator (DG) sets, the ...
Energies, 2021
Stringent environmental regulations and efforts to improve the shipping operations sustainability... more Stringent environmental regulations and efforts to improve the shipping operations sustainability have resulted in designing and employing more complex configurations for the ship power plants systems and the implementation of digitalised functionalities. Due to these systems complexity, critical situations arising from the components and subsystem failures, which may lead to accidents, require timely detection and mitigation. This study aims at enhancing the safety of ship complex systems and their operation by developing the concept of an integrated monitoring safety system that employs existing safety models and data fusion from shipboard sensors. Detailed Fault Trees that model the blackout top event, representing the sailing modes of a cruise ship and the operating modes of its plant, are employed. Shipboard sensors’ measurements acquired by the cruise ship alarm and monitoring system are integrated with these Fault Trees to account for the acquired shipboard information on the...
Proceedings of the International Seminar on Safety and Security of Autonomous Vessels (ISSAV) and European STAMP Workshop and Conference (ESWC) 2019, 2020
The adage "prevention is better than cure" is at the heart of safety principles. However, effecti... more The adage "prevention is better than cure" is at the heart of safety principles. However, effective accident prevention is challenging in complex, highly automated systems such as modern DP-driven vessels, which are supposed to safely transfer technicians in often unfavourable environmental conditions. FMEA analysis, which is required for DP-driven vessels, is helpful to build-in a necessary level of redundancy and thereby mitigate consequences of failures, but not particularly helpful to inform preventive measures, not least against functional glitches in controlling software. In this paper we develop a set of functional safety requirements which are aimed at prevention of causal factors behind drift-off, drive-off and other hazardous scenarios. For this purpose, we use a systemic hazard analysis by STPA, which delivers both failure and interaction-based (reliable-but-unsafe) scenarios. The functional requirements cover both design and operational (human element related) requirements, which are then ranked based on our proposed heuristic. The ranking is not predicated on statistics or expert option but instead it is proportional to the number of hazardous scenarios a requirement protects against, hence indicating the relative importance of the requirement. The paper also summarises the suggested areas of safety improvement for DP-driven vessels.
Every shipping company has a goal to reduce operational costs and increase income. One possible w... more Every shipping company has a goal to reduce operational costs and increase income. One possible way to achieve that is by optimizing ship's hull in respect to calm water resistance. However, because ships seldom travel at still water conditions, it is important also to introduce the effect of the added resistance in waves.
For large ships, added resistance in waves is mainly the result of wave diffraction around the ship while the added resistance due to motions has a small contribution. The available theoretical methods at the moment find it hard to evaluate accurately the diffraction component of added resistance in short waves. This makes necessary the use of semi-empirical approach or CFD methods.
Added resistance is also important for minimization of the Energy Efficiency Design Index (EEDI). Added resistance affects the selection of suitable Sea Margin and fw correction factor, which accounts for the decrease of speed in representative sea conditions. A reduction in added resistance will affect positively the EEDI.
The development of computers during last century allowed the use of parametric models created in CAD/CAE systems for representation of hulls forms. New optimization solution techniques such as Sobol functions and genetic algorithms set up the necessary background for effective and quick optimization. All of these are present in CAESES/Friendship-Framework.
In this diploma thesis, the bow of a large tanker (KVLCC2) is optimized in terms of the added resistance in waves using CAESES/Friendship-Framework for creation of parametric model and optimization. Ship's bow is also optimized for total resistance, using Holtrop-Mennen method for estimation of calm water resistance. In the last stage, ship's bow is optimized for EEDI. The resulted maximum continuous rating of ship's main engine is compared with the minimum required power in adverse conditions.
Ships operate in conditions with wind and waves most of the time and this impact must be taken in... more Ships operate in conditions with wind and waves most of the time and this impact must be taken into account during the ship's design and operation. The added resistance induced by the waves (RAW) can be classified based on the underlying physical phenomena as added resistance due ship's motions RAWM or added resistance due to waves diffraction RAWR. The impact of each component depends on special design characteristics of the ship, and also differentiates with the wave length and sea states. In this work, for operational conditions prevailed in North Atlantic, the correlation between the size of the vessel and the components of RAW was examined as well as the overall impact of the RAW on the performance of the ships, expressed by ratio of RAW over resistance in calm water (CR). For this work, simplified formulas requiring basic particulars of vessels were used. It was demonstrated that the impact of diffraction component RAWR on the RAW increases with increase of vessel size, while the ratio RAW/CR reduces, with the vessel's dimensions increasing. It was also shown, in line with previous works, that the impact of speed is also import for the RAW/CR, with this ratio increasing when the vessel's speed decreases. Last, it was also demonstrated the impact of RAW on different vessels for different sea states