H. Ren, Chen Xu, Xueqian Zhou, S. Sutulo, Carlos Soares
Sinkage and trim, which often occur to ships moving in shallow water, do not only have an effect on the ship-ship hydrodynamic interaction forces, but also increase the risk of grounding. An algorithm based on the potential theory has been devised for real-time simulation of the hydrodynamic interaction between two ships in shallow water accounting for sinkage and trim. The shallow water condition is modeled using the mirror image method; while the sinkage and trim are solved iteratively based on the principle of hydrostatic balance, where a mesh trimming procedure is performed when the waterline is changed. Simulations are performed with and without accounting for the sinkage and trim, and comparison with experimental results shows a fair agreement.
{"title":"A Numerical Method for Calculation of Ship-Ship Hydrodynamics Interaction in Shallow Water Accounting for Sinkage and Trim","authors":"H. Ren, Chen Xu, Xueqian Zhou, S. Sutulo, Carlos Soares","doi":"10.1115/omae2019-96151","DOIUrl":"https://doi.org/10.1115/omae2019-96151","url":null,"abstract":"\u0000 Sinkage and trim, which often occur to ships moving in shallow water, do not only have an effect on the ship-ship hydrodynamic interaction forces, but also increase the risk of grounding. An algorithm based on the potential theory has been devised for real-time simulation of the hydrodynamic interaction between two ships in shallow water accounting for sinkage and trim. The shallow water condition is modeled using the mirror image method; while the sinkage and trim are solved iteratively based on the principle of hydrostatic balance, where a mesh trimming procedure is performed when the waterline is changed. Simulations are performed with and without accounting for the sinkage and trim, and comparison with experimental results shows a fair agreement.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122253567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xi Chen, Wenjing Yang, Jiawei Yu, D. Feng, Wu Yongfeng
This paper studies the effect of the the caudal fin superimposed chordwise deformation on the propulsion performance. The calculation results show that the appropriate chord deformation of the caudal fin can effectively increase the propulsion efficiency. It describes the shape change of dolphin tail by mathematical formula, and studies the propulsion performance of dolphin tail by numerical method combined with morphing mesh technology. The quasi-propulsive efficiency is used to evaluate the propulsive efficiency of self-propelled objects. The results show that the active deformation of the caudal fin can effectively increase the propulsive efficiency and provide a theoretical basis for the design of the flapping bionic propeller.
{"title":"The Hydrodynamic Analysis of Dolphin Fluke Motion With a Flexible Tail","authors":"Xi Chen, Wenjing Yang, Jiawei Yu, D. Feng, Wu Yongfeng","doi":"10.1115/omae2019-95727","DOIUrl":"https://doi.org/10.1115/omae2019-95727","url":null,"abstract":"\u0000 This paper studies the effect of the the caudal fin superimposed chordwise deformation on the propulsion performance. The calculation results show that the appropriate chord deformation of the caudal fin can effectively increase the propulsion efficiency. It describes the shape change of dolphin tail by mathematical formula, and studies the propulsion performance of dolphin tail by numerical method combined with morphing mesh technology. The quasi-propulsive efficiency is used to evaluate the propulsive efficiency of self-propelled objects. The results show that the active deformation of the caudal fin can effectively increase the propulsive efficiency and provide a theoretical basis for the design of the flapping bionic propeller.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129099325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Direct numerical simulation (DNS), based on solution of the Navier Stokes equations, is used to study the characteristics of the transformation of monochromatic waves over a simplified fringing reef, including wave shoaling, and wave breaking that occurs under certain circumstances. The reef geometry involves a sloped plane beach extended with a simple submerged horizontal reef flat. The characteristics are studied for several case studies involving a selection of submergence depths on the reef flat and for a range of incident wave conditions, corresponding to nonbreaking, a spilling breaker and a plunging breaker, are considered. The results are compared with those of laboratory experiments (Kouvaras and Dhanak, 2018). Consistent with other studies, generation of harmonics of the fundamental wave frequency is found to accompany the wave transformation over the reef and the process of transfer of energy through wave breaking. The energy flux decreases dramatically in the onshore direction when the waves break. The more severe the wave breaking process, the greater the decrease in energy flux, particularly in the wave shoaling process. Most of the wave energy is carried by the first harmonic throughout its passage over the fringing reef. In nonbreaking waves, the energy gradually transfers from the first harmonic to the second harmonic due to bottom effects in terms of flat wave troughs and secondary waves. The further the distance away from the fore edge of the reef, the larger the percentage of the transmission, resulting in a single dominant harmonic frequency at the end of the wave surfing zone. For breaking waves, the energy carried by the first harmonic gradually decreases in the onshore direction. Energy transmission between harmonics is not as efficient as nonbreaking waves, while wave dissipation is significant in the wave breaking process.
{"title":"Characteristics of Transforming Waves Breaking Over a Fringing Reef","authors":"Fuxian Gong, M. Dhanak","doi":"10.1115/omae2019-96674","DOIUrl":"https://doi.org/10.1115/omae2019-96674","url":null,"abstract":"\u0000 Direct numerical simulation (DNS), based on solution of the Navier Stokes equations, is used to study the characteristics of the transformation of monochromatic waves over a simplified fringing reef, including wave shoaling, and wave breaking that occurs under certain circumstances. The reef geometry involves a sloped plane beach extended with a simple submerged horizontal reef flat. The characteristics are studied for several case studies involving a selection of submergence depths on the reef flat and for a range of incident wave conditions, corresponding to nonbreaking, a spilling breaker and a plunging breaker, are considered. The results are compared with those of laboratory experiments (Kouvaras and Dhanak, 2018). Consistent with other studies, generation of harmonics of the fundamental wave frequency is found to accompany the wave transformation over the reef and the process of transfer of energy through wave breaking. The energy flux decreases dramatically in the onshore direction when the waves break. The more severe the wave breaking process, the greater the decrease in energy flux, particularly in the wave shoaling process. Most of the wave energy is carried by the first harmonic throughout its passage over the fringing reef. In nonbreaking waves, the energy gradually transfers from the first harmonic to the second harmonic due to bottom effects in terms of flat wave troughs and secondary waves. The further the distance away from the fore edge of the reef, the larger the percentage of the transmission, resulting in a single dominant harmonic frequency at the end of the wave surfing zone. For breaking waves, the energy carried by the first harmonic gradually decreases in the onshore direction. Energy transmission between harmonics is not as efficient as nonbreaking waves, while wave dissipation is significant in the wave breaking process.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121792285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Yue, W. Kang, Wengang Mao, Pengfei Chen, Xi Wang
Floating Storage and Regasification Unit (FSRU) becomes one of the most popular equipment in the industry for providing clean energy due to its technical, economic and environmental features. Under the combined loads from wind, wave and current, it is difficult for the prediction of the dynamic response for such FSRU-LNGC (Liquified Natural Gas Carrier) side-by-side mooring system, because of the complicated hydrodynamic interaction between the two floating bodies. In this paper, a non-dimensional damping parameter of the two floating bodies is obtained from a scaled model test. Then the numerical analysis is carried out based on the test results, and the damping lid method is applied to simulate the hydrodynamic interference between floating bodies. The dynamic response of the side-by-side mooring system including six degrees of freedom motion, cable tension and fender force are provided and analyzed. According to the comparisons between numerical results and the test results, it is shown that the proposed coupled analysis model is reliable, and the numerical analysis can properly describe the dynamic response of the multi-floating mooring system in the marine environment. Moreover, the non-dimensional damping parameter which is used in numerical analysis can act as a good reference to the dynamic response analysis of similar multi-floating mooring systems.
{"title":"Experimental and Numerical Study on Dynamic Response of FSRU-LNGC Side-by-Side Mooring System","authors":"J. Yue, W. Kang, Wengang Mao, Pengfei Chen, Xi Wang","doi":"10.1115/omae2019-95473","DOIUrl":"https://doi.org/10.1115/omae2019-95473","url":null,"abstract":"\u0000 Floating Storage and Regasification Unit (FSRU) becomes one of the most popular equipment in the industry for providing clean energy due to its technical, economic and environmental features. Under the combined loads from wind, wave and current, it is difficult for the prediction of the dynamic response for such FSRU-LNGC (Liquified Natural Gas Carrier) side-by-side mooring system, because of the complicated hydrodynamic interaction between the two floating bodies. In this paper, a non-dimensional damping parameter of the two floating bodies is obtained from a scaled model test. Then the numerical analysis is carried out based on the test results, and the damping lid method is applied to simulate the hydrodynamic interference between floating bodies. The dynamic response of the side-by-side mooring system including six degrees of freedom motion, cable tension and fender force are provided and analyzed. According to the comparisons between numerical results and the test results, it is shown that the proposed coupled analysis model is reliable, and the numerical analysis can properly describe the dynamic response of the multi-floating mooring system in the marine environment. Moreover, the non-dimensional damping parameter which is used in numerical analysis can act as a good reference to the dynamic response analysis of similar multi-floating mooring systems.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127567868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Autonomous ship navigation in a mixed environment, where remote-controlled, autonomous and manned vessels are interacting, is considered. Since these vessels can have various encounter situations, adequate knowledge on such situations should be acquired to take appropriate navigation actions. That has often been categorized as situation awareness in a mixed environment, where appropriate tools and techniques to extract the respective knowledge on ship encounter situations should be developed. The collision risk assessment procedure has an important role in the same knowledge and that can eventually be used towards the respective collision avoidance actions. Hence, possible ship collision and near-miss situations can be avoided by both humans as well as systems due to their actions. Ship collision avoidance actions are regulated by the International Regulations for Preventing Collisions at Sea 1972 (COLREGs) in open sea areas and additional local navigation rules and regulations can also enforce especially in confined waters and maritime traffic lanes. It is expected that the COLREGs and other navigation rules and regulations will be interpreted by both humans as well as systems in future vessels and those interpretations will be executed as collision avoidance actions by the respective vessels in a mixed environment. Adequate understanding on situation awareness should be achieved to overcome possible regulatory failure due to human and system decisions in these situations. Hence, this study focuses on identifying such challenges in future ship encounters with possible solutions to improve situation awareness in a mixed environment as the main contribution.
{"title":"Situation Awareness of Autonomous Ship Navigation in a Mixed Environment Under Advanced Ship Predictor","authors":"L. Perera, B. Murray","doi":"10.1115/omae2019-95571","DOIUrl":"https://doi.org/10.1115/omae2019-95571","url":null,"abstract":"\u0000 Autonomous ship navigation in a mixed environment, where remote-controlled, autonomous and manned vessels are interacting, is considered. Since these vessels can have various encounter situations, adequate knowledge on such situations should be acquired to take appropriate navigation actions. That has often been categorized as situation awareness in a mixed environment, where appropriate tools and techniques to extract the respective knowledge on ship encounter situations should be developed. The collision risk assessment procedure has an important role in the same knowledge and that can eventually be used towards the respective collision avoidance actions. Hence, possible ship collision and near-miss situations can be avoided by both humans as well as systems due to their actions. Ship collision avoidance actions are regulated by the International Regulations for Preventing Collisions at Sea 1972 (COLREGs) in open sea areas and additional local navigation rules and regulations can also enforce especially in confined waters and maritime traffic lanes. It is expected that the COLREGs and other navigation rules and regulations will be interpreted by both humans as well as systems in future vessels and those interpretations will be executed as collision avoidance actions by the respective vessels in a mixed environment. Adequate understanding on situation awareness should be achieved to overcome possible regulatory failure due to human and system decisions in these situations. Hence, this study focuses on identifying such challenges in future ship encounters with possible solutions to improve situation awareness in a mixed environment as the main contribution.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122035462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Rippeth, B. Lincoln, Mattias Green, B. Scannell, Y. Lenn, V. Vlasenko, N. Stashchuk, Igor Koslov
Receding seasonal sea ice extent over the Arctic Ocean is increasing access to what was a largely inaccessible region. At lower latitudes the complex vertical current structure associated with large amplitude, high frequency non-linear internal waves, sometimes referred to as solitons, present a significant challenge to the safe engineering design and operation of offshore infrastructure. In this paper we examine the prevalence this type of internal wave in the Arctic Ocean. To do so we will draw on both in situ and remotely sensed oceanographic data. This will be combined with state-of-the-art numerical modelling to demonstrate a link between the geographical occurrence of these waves and the tide. Whilst the link implies that these features are geographically limited, it is also likely that the geographical limits will change with declining sea ice cover. These results will then be used to provide a road map towards a methodology for forecasting the prevalence of these phenomena in a future Arctic Ocean.
{"title":"The Increasing Prevalence of High Frequency Internal Waves in an Arctic Ocean With Declining Sea Ice Cover","authors":"T. Rippeth, B. Lincoln, Mattias Green, B. Scannell, Y. Lenn, V. Vlasenko, N. Stashchuk, Igor Koslov","doi":"10.1115/omae2019-96621","DOIUrl":"https://doi.org/10.1115/omae2019-96621","url":null,"abstract":"\u0000 Receding seasonal sea ice extent over the Arctic Ocean is increasing access to what was a largely inaccessible region. At lower latitudes the complex vertical current structure associated with large amplitude, high frequency non-linear internal waves, sometimes referred to as solitons, present a significant challenge to the safe engineering design and operation of offshore infrastructure. In this paper we examine the prevalence this type of internal wave in the Arctic Ocean. To do so we will draw on both in situ and remotely sensed oceanographic data. This will be combined with state-of-the-art numerical modelling to demonstrate a link between the geographical occurrence of these waves and the tide. Whilst the link implies that these features are geographically limited, it is also likely that the geographical limits will change with declining sea ice cover. These results will then be used to provide a road map towards a methodology for forecasting the prevalence of these phenomena in a future Arctic Ocean.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122289558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Numerical seakeeping codes for ships at forward speed in waves are often validated or tuned based on experiments, which makes knowledge about the experimental variability essential. This variability was evaluated using repeat tests during a state-of-the-art seakeeping campaign. A steep wave condition over the longitudinal basin axis (waveA) and a less steep oblique wave condition (waveB) were studied. Overall similarity as well as individual crest height, steepnesses and timing variability are discussed, because ship response is not equally sensitive for every point in the wave time series. The variability of the measured incoming wave crests and their timing increases with distance from the wave generator for waveA. The crest height variability for waveB is lower and more constant over the basin length (because the propagation distance to the model is constant in oblique waves and wave breaking is less likely). It was shown that only a small part of the variability close to the wave generator is caused by ‘input’ uncertainties such as the accuracy of the wave generator flap motions, measurement carriage position, their synchronisation and measurement accuracy. The rest of the variability is caused by wave and basin effects, such as wave breaking instabilities and small residual wave-induced currents from previous tests. The latter depend on previous wave conditions, which requires further study. Further work on the influence of the wave variability on the variability of ship motions, relative wave elevation along a ship and impact loads on deck of a ship at forward speed will be presented in a next publication.
{"title":"Variability in Encountered Waves During Deterministically Repeated Seakeeping Tests at Forward Speed","authors":"Sanne van Essen","doi":"10.1115/omae2019-95065","DOIUrl":"https://doi.org/10.1115/omae2019-95065","url":null,"abstract":"\u0000 Numerical seakeeping codes for ships at forward speed in waves are often validated or tuned based on experiments, which makes knowledge about the experimental variability essential. This variability was evaluated using repeat tests during a state-of-the-art seakeeping campaign.\u0000 A steep wave condition over the longitudinal basin axis (waveA) and a less steep oblique wave condition (waveB) were studied. Overall similarity as well as individual crest height, steepnesses and timing variability are discussed, because ship response is not equally sensitive for every point in the wave time series. The variability of the measured incoming wave crests and their timing increases with distance from the wave generator for waveA. The crest height variability for waveB is lower and more constant over the basin length (because the propagation distance to the model is constant in oblique waves and wave breaking is less likely).\u0000 It was shown that only a small part of the variability close to the wave generator is caused by ‘input’ uncertainties such as the accuracy of the wave generator flap motions, measurement carriage position, their synchronisation and measurement accuracy. The rest of the variability is caused by wave and basin effects, such as wave breaking instabilities and small residual wave-induced currents from previous tests. The latter depend on previous wave conditions, which requires further study.\u0000 Further work on the influence of the wave variability on the variability of ship motions, relative wave elevation along a ship and impact loads on deck of a ship at forward speed will be presented in a next publication.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125863430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents a method to predict the future trajectory of a target vessel using historical AIS data. The purpose of such a prediction is to aid in collision avoidance in future vessels. The method presented in this study extracts all trajectories present in an initial cluster centered about a vessel position. Features for each trajectory are then generated using Principle Component Analysis and used in clustering via unsupervised Gaussian mixture modeling. Each resultant cluster represents a possible future route the vessel may follow. A trajectory prediction is then conducted with respect to each cluster of trajectories discovered. This results in a prediction of multiple possible trajectories. The results indicate that the algorithm is effective in clustering the trajectories, where at least one cluster corresponds to the true trajectory of the vessel. The resultant predicted trajectories are also found to be reasonably accurate.
{"title":"An AIS-Based Multiple Trajectory Prediction Approach for Collision Avoidance in Future Vessels","authors":"B. Murray, L. Perera","doi":"10.1115/omae2019-95963","DOIUrl":"https://doi.org/10.1115/omae2019-95963","url":null,"abstract":"\u0000 This study presents a method to predict the future trajectory of a target vessel using historical AIS data. The purpose of such a prediction is to aid in collision avoidance in future vessels. The method presented in this study extracts all trajectories present in an initial cluster centered about a vessel position. Features for each trajectory are then generated using Principle Component Analysis and used in clustering via unsupervised Gaussian mixture modeling. Each resultant cluster represents a possible future route the vessel may follow. A trajectory prediction is then conducted with respect to each cluster of trajectories discovered. This results in a prediction of multiple possible trajectories. The results indicate that the algorithm is effective in clustering the trajectories, where at least one cluster corresponds to the true trajectory of the vessel. The resultant predicted trajectories are also found to be reasonably accurate.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"363 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121379449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alison K. Brown, A. Stephens, B. Rabb, Richenda K. Connell, J. Upton
While a significant amount of attention surrounding climate change has focused on mitigation of the causes, there is growing interest and need to adapt to physical climate change impacts which are already being experienced and in anticipation of future changes. Changes in climate have the potential to create hazards in the oil and gas sector although vulnerabilities to these changes are often specific to asset types. Preparedness for climate change can help to reduce damaging effects from acute as well as chronic climate changes. This paper focuses on a simple approach developed to ensure that climate change is included in engineering design, by considering climate change risk and the uncertainty inherent in future projections of climate change into design requirements. It involves using the best available climate change data and an understanding of the relationships between asset performance and environmental (climate-related) conditions. The risk level associated with climate change for a specific asset is determined by consideration of the severity and confidence level of the climate change hazard, the exposure of the asset to the hazard, the vulnerability of the exposed asset to the hazard and the capacity of the asset to adapt to the hazard. The method considers the risk levels, the selection of climate model data, the ‘natural variability’ baseline period to be applied to the climate change data, the climate change model validation, the asset life time and specifically how to modify metocean design criteria to account for climate change to ensure both the ‘start of life’ criteria (typically derived from observed and hindcast data) and ‘end of life’ criteria (including an estimate for the impact of climate change at the end of the asset life) meet the required annual probability of exceedance.
{"title":"Including the Impact of Climate Change in Offshore and Onshore Metocean Design Criteria to Ensure Asset Robustness","authors":"Alison K. Brown, A. Stephens, B. Rabb, Richenda K. Connell, J. Upton","doi":"10.1115/omae2019-95205","DOIUrl":"https://doi.org/10.1115/omae2019-95205","url":null,"abstract":"\u0000 While a significant amount of attention surrounding climate change has focused on mitigation of the causes, there is growing interest and need to adapt to physical climate change impacts which are already being experienced and in anticipation of future changes. Changes in climate have the potential to create hazards in the oil and gas sector although vulnerabilities to these changes are often specific to asset types. Preparedness for climate change can help to reduce damaging effects from acute as well as chronic climate changes. This paper focuses on a simple approach developed to ensure that climate change is included in engineering design, by considering climate change risk and the uncertainty inherent in future projections of climate change into design requirements. It involves using the best available climate change data and an understanding of the relationships between asset performance and environmental (climate-related) conditions. The risk level associated with climate change for a specific asset is determined by consideration of the severity and confidence level of the climate change hazard, the exposure of the asset to the hazard, the vulnerability of the exposed asset to the hazard and the capacity of the asset to adapt to the hazard. The method considers the risk levels, the selection of climate model data, the ‘natural variability’ baseline period to be applied to the climate change data, the climate change model validation, the asset life time and specifically how to modify metocean design criteria to account for climate change to ensure both the ‘start of life’ criteria (typically derived from observed and hindcast data) and ‘end of life’ criteria (including an estimate for the impact of climate change at the end of the asset life) meet the required annual probability of exceedance.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122846376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. A. Rodríguez, P. Esperança, Mauro Costa de Oliveira
Roll damping estimation is of great concern for the prediction of motions in waves of ship and offshore platforms, especially when viscous effects are relevant. Although this problem dates back to the times of William Froude, it has regained much attention in the context of the development of the second-generation intact stability criteria of ships, especially because there are still not accurate and efficient tools for roll damping prediction. For offshore applications, a common approach for roll damping estimation is to perform roll decay tests with scale models in calm water and then use the resultant values in the roll equation to predict motions in waves. However, for some wave conditions, the damping coefficients obtained from those tests may not be representative of the actual damping in waves. To assess the influence of wave conditions in the roll damping coefficients, the present work proposes a simplified hybrid approach that combines experimental results from model tests with numerical predictions of roll motion in waves. The numerical tool adopted here is based on a frequency domain single-degree-of-freedom model with linearized external damping that includes viscous effects. A series of experimental model tests with a typical FPSO hull in regular and irregular has been analyzed to obtain the roll damping coefficients in waves. These results are compared with those from decay tests in calm-water as well as from semi-empirical predictions based on Ikeda’s method. Despite the linearized assumption, it is expected that the damping coefficients from wave tests provide a more realistic representation of the roll dynamics than those from typical decay tests.
{"title":"Estimation of Roll Damping Coefficients Based on Model Tests Responses of a FPSO in Waves","authors":"C. A. Rodríguez, P. Esperança, Mauro Costa de Oliveira","doi":"10.1115/omae2019-96334","DOIUrl":"https://doi.org/10.1115/omae2019-96334","url":null,"abstract":"\u0000 Roll damping estimation is of great concern for the prediction of motions in waves of ship and offshore platforms, especially when viscous effects are relevant. Although this problem dates back to the times of William Froude, it has regained much attention in the context of the development of the second-generation intact stability criteria of ships, especially because there are still not accurate and efficient tools for roll damping prediction. For offshore applications, a common approach for roll damping estimation is to perform roll decay tests with scale models in calm water and then use the resultant values in the roll equation to predict motions in waves. However, for some wave conditions, the damping coefficients obtained from those tests may not be representative of the actual damping in waves. To assess the influence of wave conditions in the roll damping coefficients, the present work proposes a simplified hybrid approach that combines experimental results from model tests with numerical predictions of roll motion in waves. The numerical tool adopted here is based on a frequency domain single-degree-of-freedom model with linearized external damping that includes viscous effects. A series of experimental model tests with a typical FPSO hull in regular and irregular has been analyzed to obtain the roll damping coefficients in waves. These results are compared with those from decay tests in calm-water as well as from semi-empirical predictions based on Ikeda’s method. Despite the linearized assumption, it is expected that the damping coefficients from wave tests provide a more realistic representation of the roll dynamics than those from typical decay tests.","PeriodicalId":124589,"journal":{"name":"Volume 7B: Ocean Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125862818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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