Dave Chen Lung Chong, A. S. Suhaili, S. M. Ng, Wan Hariz Fadli Wan Shafie, Biramarta Isnadi, R. Khan, K. Lau, Nurzarina Hassan, M. F. B. Ismail
Mini Remotely Operated Vehicle (mini-ROV) technology has been utilized to perform underwater inspection with optimized Risk-based Underwater Inspection (RBUI) scope for offshore platforms which conventionally utilize divers and ROV supported by Dynamic Positioning II Diving Support Vessel (DPII DSV). This offshore technology was introduced by launching mini-ROV from platform deck to perform General Visual Inspection (GVI), Cathodic Potential (CP) Survey, Flooded Member Detection (FMD) & Ultrasonic Thickness (UT) measurement with customized mini-ROV integration with other tooling. The small size ROV is light and easy to handle by technician onboard platform deck. It is also capable to enter congested areas as it is easily maneuvered, which help to capture close visual of the findings. During emergency, the mini-ROV can be mobilized instantly at site to support any GVI related scope. PETRONAS has successfully deployed this technology at four platforms in one of the operating regions from 2017 to 2021 with cost saving of 30%–50% compared to conventional method. The successful implementation in PETRONAS can become benchmark and reference for other Oil & Gas operators as an alternative to conduct optimized RBUI scope which can contribute to lower Operating Expenditure (OPEX).
{"title":"Vessel-Less Underwater Inspection at Fixed Offshore Structure by Utilizing Mini Remotely Operated Vehicle (Mini-ROV)","authors":"Dave Chen Lung Chong, A. S. Suhaili, S. M. Ng, Wan Hariz Fadli Wan Shafie, Biramarta Isnadi, R. Khan, K. Lau, Nurzarina Hassan, M. F. B. Ismail","doi":"10.1115/omae2022-81373","DOIUrl":"https://doi.org/10.1115/omae2022-81373","url":null,"abstract":"\u0000 Mini Remotely Operated Vehicle (mini-ROV) technology has been utilized to perform underwater inspection with optimized Risk-based Underwater Inspection (RBUI) scope for offshore platforms which conventionally utilize divers and ROV supported by Dynamic Positioning II Diving Support Vessel (DPII DSV). This offshore technology was introduced by launching mini-ROV from platform deck to perform General Visual Inspection (GVI), Cathodic Potential (CP) Survey, Flooded Member Detection (FMD) & Ultrasonic Thickness (UT) measurement with customized mini-ROV integration with other tooling. The small size ROV is light and easy to handle by technician onboard platform deck. It is also capable to enter congested areas as it is easily maneuvered, which help to capture close visual of the findings. During emergency, the mini-ROV can be mobilized instantly at site to support any GVI related scope. PETRONAS has successfully deployed this technology at four platforms in one of the operating regions from 2017 to 2021 with cost saving of 30%–50% compared to conventional method. The successful implementation in PETRONAS can become benchmark and reference for other Oil & Gas operators as an alternative to conduct optimized RBUI scope which can contribute to lower Operating Expenditure (OPEX).","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91343327","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}
Side-by-side offloading between two vessels in offshore operations, creates a narrow gap where blistering free surface motions may be excited due to resonant responses. The present study investigates what influence gap width and artificial damping has on these motions. We run a series of numerical simulations, based on a 3D linear potential flow solver using a numerically validated model from our previous work. The model is meant to simulate a floating liquefied natural gas (FLNG) facility, an LNG carrier, and the narrow gap created between them. In this study, the resonant fluid motions in the gap are investigated based on a configuration where both vessels are fixed. The results show a significant impact on the response of the gap resonance with diverse gap widths. By applying artificial damping to the free surface, we found that there is no significant effect on the resonant motions of the gap surface after the gap width reaches a significant fraction of one ship breadth.
{"title":"Influence of Gap Width and Artificial Damping on Gap Resonance","authors":"Ivan Ekerhovd, M. Ong, Wenhua Zhao","doi":"10.1115/omae2022-80758","DOIUrl":"https://doi.org/10.1115/omae2022-80758","url":null,"abstract":"\u0000 Side-by-side offloading between two vessels in offshore operations, creates a narrow gap where blistering free surface motions may be excited due to resonant responses. The present study investigates what influence gap width and artificial damping has on these motions. We run a series of numerical simulations, based on a 3D linear potential flow solver using a numerically validated model from our previous work. The model is meant to simulate a floating liquefied natural gas (FLNG) facility, an LNG carrier, and the narrow gap created between them. In this study, the resonant fluid motions in the gap are investigated based on a configuration where both vessels are fixed. The results show a significant impact on the response of the gap resonance with diverse gap widths. By applying artificial damping to the free surface, we found that there is no significant effect on the resonant motions of the gap surface after the gap width reaches a significant fraction of one ship breadth.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85466612","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}
Calculation of wave drift forces in the context of mooring analysis is usually performed by potential flow boundary element methods. For monohulls with large waterplane area, such as floating, production, storage and offloading vessels (FPSOs), the assumption is that heave and pitch damping is dominated by inviscid radiation of waves. The present study investigates the effects of heave and pitch wave frequency viscous damping on the horizontal wave drift forces of a FPSO. Experimental evidence indicates the presence of non-negligible viscous damping in case of moderate and severe seastates. Such observation is confirmed by computational fluid dynamic (CFD) simulations of forced harmonic motions with different periods and amplitudes. On a second step, a numerical analysis shows that the surge wave drift forces increase significantly at the low frequency range when realistic heave and pitch viscous damping is considered. The frequency range where standard potential flow calculations appear to underestimate wave drift forces coincides with the range where design seastates have most of the energy. Finally, the wave drift coefficients calculated with realistic additional viscous damping are compared with empirical coefficients identified from model test data. The identification procedure follows a second order signal analysis technique known as cross bi spectral analysis.
{"title":"Increase of Wave Drift Forces in Severe Seastates Due to Wave Frequency Viscous Damping","authors":"N. Fonseca, Babak Ommani","doi":"10.1115/omae2022-81461","DOIUrl":"https://doi.org/10.1115/omae2022-81461","url":null,"abstract":"\u0000 Calculation of wave drift forces in the context of mooring analysis is usually performed by potential flow boundary element methods. For monohulls with large waterplane area, such as floating, production, storage and offloading vessels (FPSOs), the assumption is that heave and pitch damping is dominated by inviscid radiation of waves. The present study investigates the effects of heave and pitch wave frequency viscous damping on the horizontal wave drift forces of a FPSO. Experimental evidence indicates the presence of non-negligible viscous damping in case of moderate and severe seastates. Such observation is confirmed by computational fluid dynamic (CFD) simulations of forced harmonic motions with different periods and amplitudes. On a second step, a numerical analysis shows that the surge wave drift forces increase significantly at the low frequency range when realistic heave and pitch viscous damping is considered. The frequency range where standard potential flow calculations appear to underestimate wave drift forces coincides with the range where design seastates have most of the energy. Finally, the wave drift coefficients calculated with realistic additional viscous damping are compared with empirical coefficients identified from model test data. The identification procedure follows a second order signal analysis technique known as cross bi spectral analysis.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83332197","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}
Q. Sourisseau, Emilie Leprêtre, S. Chataigner, X. Chapeleau, L. Mouton, S. Paboeuf
In tropical areas, with marine environment, high temperature and humidity, corrosion is a constant threat. The maintenance of steel structures (like FPSO’s) is becoming a challenge. The current technique of “crop and renewing” repair involves a certain number of major issues for project owners such as: “hot work”, that is to say welding; temporary weakening of the structure; need to empty, clean and purging the oil tanks of the FPSO’s, resulting in long downtime and an expensive solution. “Cold repair”, such as composite repair, is a promising solution. However, surface preparation and the influence of the primer are crucial issues to be addressed to ensure the strength and reliability of this type solution based on bonded patch. The paper presents an experimental study of the influence of the surface preparation and the primer on the strength of small steel bonded specimens which have been deliberately degraded by corrosion and pollution. Several surface preparation methodologies were investigated and the quality of these preparations was assessed using methods that can be implemented on site. Two main aspects were investigated: the detection of the residual presence of pollutants through the use of a portable infrared spectrometer; and the determination of surface energy after preparation using contact angle and wettability measurement equipment. To study the impact of the primer on the adhesion capacity of the steel surface, critical toughnesses measurements was performed with End notch flexure tests. Three configurations have been tested: bonding with the epoxy resin without initial application of primer and bonding with the Epoxy resin with initial application of two Primer A and B. The results shown clearly that the type of primer and the quality of its application are paramount importance to ensure the strength of steel bonded patches.
{"title":"Adhesively Bonded FRP Reinforcement of Steel Structures: Surface Preparation Analysis and Influence of the Primer","authors":"Q. Sourisseau, Emilie Leprêtre, S. Chataigner, X. Chapeleau, L. Mouton, S. Paboeuf","doi":"10.1115/omae2022-79079","DOIUrl":"https://doi.org/10.1115/omae2022-79079","url":null,"abstract":"\u0000 In tropical areas, with marine environment, high temperature and humidity, corrosion is a constant threat. The maintenance of steel structures (like FPSO’s) is becoming a challenge. The current technique of “crop and renewing” repair involves a certain number of major issues for project owners such as: “hot work”, that is to say welding; temporary weakening of the structure; need to empty, clean and purging the oil tanks of the FPSO’s, resulting in long downtime and an expensive solution. “Cold repair”, such as composite repair, is a promising solution. However, surface preparation and the influence of the primer are crucial issues to be addressed to ensure the strength and reliability of this type solution based on bonded patch.\u0000 The paper presents an experimental study of the influence of the surface preparation and the primer on the strength of small steel bonded specimens which have been deliberately degraded by corrosion and pollution. Several surface preparation methodologies were investigated and the quality of these preparations was assessed using methods that can be implemented on site. Two main aspects were investigated: the detection of the residual presence of pollutants through the use of a portable infrared spectrometer; and the determination of surface energy after preparation using contact angle and wettability measurement equipment. To study the impact of the primer on the adhesion capacity of the steel surface, critical toughnesses measurements was performed with End notch flexure tests. Three configurations have been tested: bonding with the epoxy resin without initial application of primer and bonding with the Epoxy resin with initial application of two Primer A and B. The results shown clearly that the type of primer and the quality of its application are paramount importance to ensure the strength of steel bonded patches.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85379710","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 work investigates the use of open architectures to support the development of flexible and scalable maritime design web applications, giving stakeholders shared access to data. It turns to the popular full-stack MERN architecture (MongoDB, Node.js, Express, and React), which is is modular and mostly open source. A prototype web application providing features for ship design and operation was developed. The app stores a ship model which can be linked to different analyses and simulations. During design, users might opt to visualize the model of the ship with a spatial view; during operation, they can resort to a detailed visualization displaying the vessel as built. Three examples are provided to illustrate the potential of these features. First, a dashboard displaying results for hydrostatics, stability, resistance, and motion response. The second use case hypothesizes a vessel is set to undergo a jumboization procedure and compares the analyses results for the vessel after elongation with the current ones. The third exemplifies how a preliminary maneuvering model can be confronted with results from a sea trial by linking the app to operational data, a step towards digital-twin concepts. The discussion addresses the potential of the approach and challenges that need to be considered before extending it to an application that can be used outside the academia.
{"title":"Applying Open Web Architectures Towards Collaborative Maritime Design and Simulation","authors":"Felipe F. de Oliveira, Í. A. Fonseca, H. Gaspar","doi":"10.1115/omae2022-81505","DOIUrl":"https://doi.org/10.1115/omae2022-81505","url":null,"abstract":"\u0000 This work investigates the use of open architectures to support the development of flexible and scalable maritime design web applications, giving stakeholders shared access to data. It turns to the popular full-stack MERN architecture (MongoDB, Node.js, Express, and React), which is is modular and mostly open source. A prototype web application providing features for ship design and operation was developed. The app stores a ship model which can be linked to different analyses and simulations. During design, users might opt to visualize the model of the ship with a spatial view; during operation, they can resort to a detailed visualization displaying the vessel as built. Three examples are provided to illustrate the potential of these features. First, a dashboard displaying results for hydrostatics, stability, resistance, and motion response. The second use case hypothesizes a vessel is set to undergo a jumboization procedure and compares the analyses results for the vessel after elongation with the current ones. The third exemplifies how a preliminary maneuvering model can be confronted with results from a sea trial by linking the app to operational data, a step towards digital-twin concepts. The discussion addresses the potential of the approach and challenges that need to be considered before extending it to an application that can be used outside the academia.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74269036","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}
The development of the offshore oil and gas industry has been experienced for more than a century and many offshore facilities are facing the decommissioning challenge. For the reason of offshore facilities are in a harsh ocean environment, the risk assessment and accidental warning technologies involved in the decommissioning process causes attention by industry and academia. Due to the characteristic of high-impact low-probability, domino effect accidents are required to be assessed by the European Union’s Seveso-II Directive, especially when considering the chemical industry risk assessment. However, at present, there is few risks assessment system for the decommissioning of offshore oil and gas facilities. This paper presents a study on the establishment of a Domino Effect risk assessment system for offshore oil and gas facilities’ decommissioning. Compared with the traditional risk assessment system which only conducts a unilateral assessment of certain hazards, this Domino effect risk assessment system combines 7 major hazards with 9 decommissioning procedures in 2 event layers. Meanwhile, a domino event trigger mechanism has been established. The proposed system uses theoretical equations to assess the risks assessment results quickly and accurately.
{"title":"Domino Effect Risk Assessment System for Offshore Oil and Gas Facilities Decommissioning","authors":"Yihong Li, Zhiqian Hu","doi":"10.1115/omae2022-78196","DOIUrl":"https://doi.org/10.1115/omae2022-78196","url":null,"abstract":"\u0000 The development of the offshore oil and gas industry has been experienced for more than a century and many offshore facilities are facing the decommissioning challenge. For the reason of offshore facilities are in a harsh ocean environment, the risk assessment and accidental warning technologies involved in the decommissioning process causes attention by industry and academia. Due to the characteristic of high-impact low-probability, domino effect accidents are required to be assessed by the European Union’s Seveso-II Directive, especially when considering the chemical industry risk assessment. However, at present, there is few risks assessment system for the decommissioning of offshore oil and gas facilities.\u0000 This paper presents a study on the establishment of a Domino Effect risk assessment system for offshore oil and gas facilities’ decommissioning. Compared with the traditional risk assessment system which only conducts a unilateral assessment of certain hazards, this Domino effect risk assessment system combines 7 major hazards with 9 decommissioning procedures in 2 event layers. Meanwhile, a domino event trigger mechanism has been established. The proposed system uses theoretical equations to assess the risks assessment results quickly and accurately.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84058327","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}
Csaba Pákozdi, Eloise Croonenborghs, Jang-Whan Kim, M. Peric, G. Ducrozet, B. Bouscasse, Haihua Xu, A. Califano, A. Akselsen, Sébastien Loubeyre
In 2020, a modeling practice was presented to perform numerical simulation of waves, where waves generated by a numerical wave tank (NWT) were used as input to a CFD simulation. This paper presents an extension of those practices in the context of wave impact on a gravity-based structure (GBS). It focuses on capturing accurate wave loads for a prescribed wave event, reproduced from a measured time series. This modeling practice serves the purpose that if it is followed by a CFD practitioner, the CFD results are reproducible. The modeling practice is validated for two regular wave cases and one irregular wave event. The validation data are based on experiments performed at MARINTEK in model scale 1:54 with the water depth 2.81m. During the validation the wave time series are compared against model test without and with GBS at scale 1:54. Further, relative wave height time series, global forces and moments acting on the deck as well as slamming forces are compared against model test records. The modeling practice is validated with Simcenter STAR-CCM+ as the main CFD solution but the modeling strategy can be applied to other CFD software. Thanks to the initialization of the CFD solution with user defined waves (UDW), the NWT-CFD coupling shows two advantages. First, the size of the CFD domain can be reduced to a minimum. Second, it is sufficient to start the CFD simulation shortly before the impact event.
{"title":"Joint-Industry Effort to Develop and Verify CFD Modeling Practice for Predicting Wave Impact","authors":"Csaba Pákozdi, Eloise Croonenborghs, Jang-Whan Kim, M. Peric, G. Ducrozet, B. Bouscasse, Haihua Xu, A. Califano, A. Akselsen, Sébastien Loubeyre","doi":"10.1115/omae2022-79152","DOIUrl":"https://doi.org/10.1115/omae2022-79152","url":null,"abstract":"\u0000 In 2020, a modeling practice was presented to perform numerical simulation of waves, where waves generated by a numerical wave tank (NWT) were used as input to a CFD simulation. This paper presents an extension of those practices in the context of wave impact on a gravity-based structure (GBS). It focuses on capturing accurate wave loads for a prescribed wave event, reproduced from a measured time series. This modeling practice serves the purpose that if it is followed by a CFD practitioner, the CFD results are reproducible.\u0000 The modeling practice is validated for two regular wave cases and one irregular wave event. The validation data are based on experiments performed at MARINTEK in model scale 1:54 with the water depth 2.81m. During the validation the wave time series are compared against model test without and with GBS at scale 1:54. Further, relative wave height time series, global forces and moments acting on the deck as well as slamming forces are compared against model test records. The modeling practice is validated with Simcenter STAR-CCM+ as the main CFD solution but the modeling strategy can be applied to other CFD software.\u0000 Thanks to the initialization of the CFD solution with user defined waves (UDW), the NWT-CFD coupling shows two advantages. First, the size of the CFD domain can be reduced to a minimum. Second, it is sufficient to start the CFD simulation shortly before the impact event.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74343804","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}
The semisubmersible platform (Semi) shows superior performance to the Spar, TLP and FPSO owing to its unique and reasonable structure and shape, and thus is one of the most vital and promising equipment for deepsea oil and gas development. Nevertheless, its inherent disadvantages have been gradually revealed through six decades of extensive engineering practices and in-depth research. Much innovative work has been carried out during recent two decades to improve its overall performance and maximize its safety and operability to utilize it in supervisor ways. Firstly, the shape features of a conventional Semi and the operation requirements in different phases during the whole life cycle of a Semi were summarized. Then, the factors affecting the stability and the motion performance of a Semi and their internal relationship were studied according to the principles of hydrostatics and hydrodynamics. After that, representative innovative conceptual Semi designs in the academic papers and the patent documents were reviewed. Finally, the directions for further innovation and growth of the Semi were predicted. This paper aims to provide some inspiration and reference to the experts and scholars engaged in deepwater offshore field development and innovative research on the floating structures.
{"title":"State of the Art in New Semisubmersible Platform Concepts","authors":"Tianying Wang, Qing Cui","doi":"10.1115/omae2022-81085","DOIUrl":"https://doi.org/10.1115/omae2022-81085","url":null,"abstract":"\u0000 The semisubmersible platform (Semi) shows superior performance to the Spar, TLP and FPSO owing to its unique and reasonable structure and shape, and thus is one of the most vital and promising equipment for deepsea oil and gas development. Nevertheless, its inherent disadvantages have been gradually revealed through six decades of extensive engineering practices and in-depth research. Much innovative work has been carried out during recent two decades to improve its overall performance and maximize its safety and operability to utilize it in supervisor ways. Firstly, the shape features of a conventional Semi and the operation requirements in different phases during the whole life cycle of a Semi were summarized. Then, the factors affecting the stability and the motion performance of a Semi and their internal relationship were studied according to the principles of hydrostatics and hydrodynamics. After that, representative innovative conceptual Semi designs in the academic papers and the patent documents were reviewed. Finally, the directions for further innovation and growth of the Semi were predicted. This paper aims to provide some inspiration and reference to the experts and scholars engaged in deepwater offshore field development and innovative research on the floating structures.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91061472","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}
Model test campaigns conducted recent years indicate large wave impact loads on vertical surfaces above the waterline for various types of moored floating structures. The basis for the estimate of characteristic loads is typically slamming pressure measured on a grid of slamming panels. In order to validate the measurements of slamming pressure, drop tests for a slamming section used in slamming tests (see [1] and [2]) have been conducted. The section was dropped in a small water basin at different configurations to resemble impacts from waves with varying front steepness and velocity of wave front. In Lian et al [3], most of the results from the drop tests were presented and compared to theoretical solutions. It was concluded that the peak slamming coefficient is close to the expected theoretical value, but for small impact angles the load measured during the drop becomes significantly lower than theoretical observations and previous tests results, e.g. by Campbell and Weynberg [4]. Possible sources of errors in the tests may be retardation/change of velocity during impact or effect of 3D flow in drop. In the work presented in this paper these findings have been investigated further. An alternative drop test using a cylinder with smaller diameter, and neglectable effect from 3D flow, has been carried out. Numerical simulations of the drop tests, where effect of retardation is accounted for, have been conducted. In November 2019, the drop test with the slamming section was repeated and the mass of the section was varied to study the effect of retardation. In the present paper results from drop tests and numerical calculations are compared and findings are reported.
{"title":"Validation of Measurement Techniques Used for Slamming","authors":"O. Økland, G. Lian, Tone M. Vestbøstad","doi":"10.1115/omae2022-79068","DOIUrl":"https://doi.org/10.1115/omae2022-79068","url":null,"abstract":"\u0000 Model test campaigns conducted recent years indicate large wave impact loads on vertical surfaces above the waterline for various types of moored floating structures. The basis for the estimate of characteristic loads is typically slamming pressure measured on a grid of slamming panels.\u0000 In order to validate the measurements of slamming pressure, drop tests for a slamming section used in slamming tests (see [1] and [2]) have been conducted. The section was dropped in a small water basin at different configurations to resemble impacts from waves with varying front steepness and velocity of wave front. In Lian et al [3], most of the results from the drop tests were presented and compared to theoretical solutions. It was concluded that the peak slamming coefficient is close to the expected theoretical value, but for small impact angles the load measured during the drop becomes significantly lower than theoretical observations and previous tests results, e.g. by Campbell and Weynberg [4]. Possible sources of errors in the tests may be retardation/change of velocity during impact or effect of 3D flow in drop.\u0000 In the work presented in this paper these findings have been investigated further. An alternative drop test using a cylinder with smaller diameter, and neglectable effect from 3D flow, has been carried out. Numerical simulations of the drop tests, where effect of retardation is accounted for, have been conducted. In November 2019, the drop test with the slamming section was repeated and the mass of the section was varied to study the effect of retardation. In the present paper results from drop tests and numerical calculations are compared and findings are reported.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86539146","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}
Originally developed for civil engineering applications, the tuned liquid column damper (TLCD) has been applied not only on tall buildings but also on floating offshore wind turbines (FOWTs) to minimize structural vibrations. This concept has also been adopted widely in navel architecture to reduce the roll motion. However, whether the damper will bring positive effects on mitigating the dynamic motions of FOWTs remains unknown. To this end, the paper studies the star-like three columns tuned liquid multi-column damper (TLMCD) impacts on the dynamic motions of a semi-submersible FOWT. The modelling is achieved by using a high-fidelity computational fluid dynamic (CFD) solver based on OpenFOAM. After the verification of the numerical model for the TLMCD system, it is extended to the modelling of the internal sloshing of TLMCD under prescribed pitch motions. A fully coupled floating-sloshing modelling is then conducted to simulate a semi-submersible FOWT with an integrated TLMCD under regular wave conditions. The study indicates that the passive-control TLMCD system has nearly no influence on the translational motions such as surge and heave. However, the pitch motions can be reduced significantly when the incident wave frequency is close to the natural pitch frequency of the platform. Apart from the natural pitch frequency, the TLMCD has a minor effect at other incident wave frequencies.
{"title":"Investigations On The Effects Of Internal Liquid Sloshing of Semi-Submersible Floating Offshore Wind Turbines","authors":"Yang Zhou, L. Qian, W. Bai, Zaibin Lin","doi":"10.1115/omae2022-79942","DOIUrl":"https://doi.org/10.1115/omae2022-79942","url":null,"abstract":"\u0000 Originally developed for civil engineering applications, the tuned liquid column damper (TLCD) has been applied not only on tall buildings but also on floating offshore wind turbines (FOWTs) to minimize structural vibrations. This concept has also been adopted widely in navel architecture to reduce the roll motion. However, whether the damper will bring positive effects on mitigating the dynamic motions of FOWTs remains unknown.\u0000 To this end, the paper studies the star-like three columns tuned liquid multi-column damper (TLMCD) impacts on the dynamic motions of a semi-submersible FOWT. The modelling is achieved by using a high-fidelity computational fluid dynamic (CFD) solver based on OpenFOAM. After the verification of the numerical model for the TLMCD system, it is extended to the modelling of the internal sloshing of TLMCD under prescribed pitch motions. A fully coupled floating-sloshing modelling is then conducted to simulate a semi-submersible FOWT with an integrated TLMCD under regular wave conditions. The study indicates that the passive-control TLMCD system has nearly no influence on the translational motions such as surge and heave. However, the pitch motions can be reduced significantly when the incident wave frequency is close to the natural pitch frequency of the platform. Apart from the natural pitch frequency, the TLMCD has a minor effect at other incident wave frequencies.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76364327","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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