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K. Ouchi - One of the best experts on this subject based on the ideXlab platform.
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Results From Real Sea Experiment of Ocean Nutrient Enhancer TAKUMI
Volume 4: Ocean Engineering; Ocean Renewable Energy; Ocean Space Utilization Parts A and B, 2009Co-Authors: K. OuchiAbstract:Upwelling and scattering Deep Ocean Water (DOW) into the euphotic surface layer has been proposed by many oceanographers as a “fishing ground of artificial upwelling”. So far, however, there are no successful means to make it, because of the following difficulties; the very huge amount of DOW upwelling, the dilution of DOW’s nutrient salts in the sea, enduring the rough sea condition on offshore, the strength of very long Riser pipe for upwelling, etc. The MARINO-FORUM 21, sponsored by Japanese government fisheries agency, organized the research and development project of an ocean nutrient enhancer named TAKUMI and real sea experiment using it, since the year of 2000. New technology concept, featuring the density current generator for avoiding dilution of nutrient salts, the spar type submersible floating structure for withstanding against the rough sea condition, and the design and analysis of Riser pipe for not only in case of the rough sea but also in case of the upending which is world first challenge of election of Steel Riser pipe with gravity fall in the sub-sea, was studied and introduced for the design of TAKUMI as a proper Ocean Nutrient Enhancer. TAKUMI that upwells DOW of 100,000m3/day from 200m depth and discharges it into the euphotic layer with Diesel engine was manufactured and set-up at the center of Sagami Bay in Japan, in May 2003. More than five years continuous operation in various sea conditions, which includes very rough sea in typhoon and rapid current, caused by direction change of Kuroshio Current was carried out. Also, the behavior of the nutrient water mass and the pattern of primary production around TAKUMI was investigated using the research vessel Tansei Maru. The results from the real sea experiment lead us to believe that the TAKUMI type artificial DOW upwelling system can be feasible to increase a primary production and make a fishing ground in case of large size system of more than 1,000,000m3/day.
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Design concept and experiment of ocean nutrient enhancer "TAKUMI"
Oceans '04 MTS IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600), 2004Co-Authors: K. Ouchi, H. OhmuraAbstract:To increase a primary production in the sea, upwelling and discharging a Deep Ocean Water (DOW) which has very rich nutrient salts into the euphotic surface layer has been proposed by many oceanologists as a "fishing ground of artificial DOW upwelling". But, so far, there are no successful means to make it, because of the problems of the large amount of upwelling DOW, the dilution of nutrient salts in the sea, enduring the rough sea condition, the strength of very long Riser pipe for upwelling, etc. The design concept of ocean nutrient enhancer TAKUMI, featuring the density current for avoiding the dilution of nutrient salts, the spar type submersible floating structure for withstanding the rough sea condition, and the design and analysis of Riser pipe for not only in case of rough sea but also in case of the upending which is world first challenge of election of Steel Riser pipe with gravity fall in the subsea, is introduced. Also, about one year continuous running operation of TAKUMI and the investigation results of the water mass discharged from TAKUMI are reported.
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Real sea experiment of ocean nutrient enhancer "TAKUMI" upwelling deep ocean water
Oceans 2003. Celebrating the Past ... Teaming Toward the Future (IEEE Cat. No.03CH37492), 2003Co-Authors: K. Ouchi, A.j. MurphyAbstract:The five years project of increasing a primary production and making a new fishing ground by upwelling deep ocean water (DOW) which is very rich in nutrient salt such as Nitrogen, Phosphorus, etc. was commenced in the year of 2000, sponsored by the Fisheries Agency of Japanese Government and Marino-Forum 21. In the open ocean, now, there are no successful means to upwell DOW artificially and to make a fishing ground. Therefore, the focus of the project is a creation and proposition of the concept of Ocean Nutrient Enhancer (ONE) to contribute for increasing primary productions and fish productions, furthermore, conducting the experiment in actual sea to confirm the effect of the ONE. The requisite technologies for the ONE such as a density current diffusion, a spar type floating structure, a Steel Riser pipe, a set-up way of upending, etc. is discussed and integrated to create prototype of ONE, whose specifications are the DOW upwelling capacity of 100,000m3/day, the displacement of about l,700tons, Diesel engine of 100KW. The ONE will be set-up with the single point mooring system at the centre of rotational flow in Sagami Bay in the depth of about 1,000m, in May 2003. In this paper, the outline of the prototype of ONE which is named "TAKUMI" is introduced.
Clóvis De Arruda Martins - One of the best experts on this subject based on the ideXlab platform.
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Comparison of Different Approaches for Fatigue Damage Accumulation in Steel Risers
Volume 4: Pipeline and Riser Technology, 2011Co-Authors: Fernanda Cristina De Moraes Takafuji, Clóvis De Arruda MartinsAbstract:Fatigue is one of the main concerns of the offshore industry nowadays, since the failure of equipments could put not only the environment but also some people’s lives in danger. As described in DNV-RP-C203 and in DNV-RP-F204, the aim of fatigue analysis is to verify if a certain structure — in this case, a Riser — will be able to operate adequately during a desired period of time, as well as to obtain information to program inspections. In a Riser, the efforts vary along its length and also around its circumference. If one considers the stress around the circumference, the maximum stress point may change. To be realistic, one approach is to calculate the stress and fatigue life around the circumference. To be more conservative and also simplify the calculation, one could consider that the maximum stress always occurs at the same point. The purpose of this paper is to compare the fatigue life obtained with both approaches in order to verify the differences between them and verify how conservative that simplification can be. To perform the task, a Steel Riser is considered and the dynamic analysis is executed in time domain using Orcaflex 9.4. The fatigue is analyzed through the S-N Curve approach and the Miner’s rule is used to accumulate the damage.Copyright © 2011 by ASME
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Parallel Dynamic Optimization of Steel Risers
Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme, 2010Co-Authors: Rafael Loureiro Tanaka, Clóvis De Arruda MartinsAbstract:This paper addresses the use of optimization techniques in the design of a Steel Riser. Two methods are used: the genetic algorithm, which imitates the process of natural selection, and the simulated annealing, which is based on the process of annealing of a metal. Both of them are capable of searching a given solution space for the best feasible Riser configuration according to predefined criteria. Optimization issues are discussed, such as problem codification, parameter selection, definition of objective function, and restrictions. A comparison between the results obtained for economic and structural objective functions is made for a case study. Optimization method parallelization is also addressed.
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Parallel Dynamic Optimization of Steel Risers
Volume 3: Pipeline and Riser Technology; Ocean Space Utilization, 2008Co-Authors: Rafael Loureiro Tanaka, Clóvis De Arruda MartinsAbstract:The design of an ultradeepwater Steel Riser is known to be a challenging task, considering the several environmental load conditions to be simulated and the long time took by each simulation. To aid in this task, optimization algorithms can be used to automate the search for the best design. The problem, however, is very expensive computationally, motivating the implementation and use of a parallel optimization software coupled with a frequency domain dynamic model. This paper deals with the use of two algorithms to optimize a Steel Riser of given inner diameter and material for both pipe and floater: the genetic algorithm and the simulated annealing. The optimizer is left free to vary the length of the segments and the floater diameter, inside user-defined ranges. Each obtained configuration is tested in a set of load cases with different currents, offsets and waves. Optimization times and performance gain with parallelization is addressed for both algorithms.© 2008 ASME
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a genetic algorithm approach to Steel Riser optimization
Volume 1: Offshore Technology; Offshore Wind Energy; Ocean Research Technology; LNG Specialty Symposium, 2006Co-Authors: Rafael Loureiro Tanaka, Clóvis De Arruda MartinsAbstract:It is well known that the Riser system represents an important part of a production unit’s total cost. To ensure economic feasibility it is important to find means to reduce this cost to its minimum. In order to achieve cost reduction and other design improvements, optimization algorithms have been used in several areas with great success. This paper presents the application of such an algorithm, known as Genetic Algorithm, to the optimization of a Steel Riser taking into account material and installation costs. From a given inner diameter and material for both pipe and floater, the optimizer is left free to vary the number of segments as well as the pipe thickness, length and floater diameter for each segment, inside user-defined ranges. Each obtained configuration is tested in a set of load cases with different currents and offsets. Restrictions such as maximum tension, minimum curvature radius and maximum stress are applied to verify the configurations’ feasibility. Only static analysis is performed.Copyright © 2006 by ASME
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Parametric Analysis of a Lazy-Wave Steel Riser
24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 1 Parts A and B, 2005Co-Authors: Francisco Edward Roveri, Clóvis De Arruda Martins, Rosianita BalenaAbstract:Lazy-wave Steel Risers appear as a possible solution for ultra deepwater oil fields in Campos Basin. The design of such a solution, however, is a very time consuming task as several configurations must be studied, including static, dynamic and fatigue analysis. In the first cycle of design, simplified models can be used to speed up the selection process of feasible configurations. This paper presents a parametric analysis that was implemented on a computer tool, aiming to select the feasible geometric configurations for a lazy-wave Steel Riser in the first cycle of design.© 2005 ASME
Rajeev K. Jaiman - One of the best experts on this subject based on the ideXlab platform.
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A comprehensive study on composite Risers: Material solution, local end fitting design and global response
Marine Structures, 2018Co-Authors: Rajeev K. JaimanAbstract:Abstract Two up-to-date composite Riser solutions, specifically, the thermoset and thermoplastic based ones are studied in a global-local framework to examine their technical feasibility for offshore applications. At the local scale, the Riser pipe body with multi-layered structure is homogenized through an analytical approach, obtaining equivalent material properties of the Riser string model for the global analysis. The metal-composite interface (MCI) end fittings between the Riser body and standard connector are examined using finite element (FE) simulations to understand their load-transfer mechanisms for both solutions. At the global scale, an in-house analysis code is performed to study the Risers' static and dynamic response in a certain sea condition due to top-tension, current drag and vortex induced vibration (VIV). The analyzed parameters include the resulting Riser deflection, axial stress, tension and bending moment distributions. Following that, an integrated analysis utilizing the global results and the local failure envelopes is performed to determine if the maximum stress states of the Riser exceed the equivalent structural strength boundary. It is concluded that composite Risers exhibit a larger safety margin than traditional Steel Riser under the same sea condition.
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Coupled fluid–structure simulations for evaluating a performance of full-scale deepwater composite Riser
Ocean Engineering, 2015Co-Authors: Yu Chen, Rajeev K. JaimanAbstract:Abstract A global–local analysis methodology based on fluid–structure coupling is used to investigate the mechanical responses of both composite and Steel Risers. Since the design of the Riser system can be a daunting task, involving hundreds of load cases for global analysis, semi-empirical fluid load models are considered for the reduced order computations of full-scale Riser models. The structural performance of composite Risers under real sea current conditions is investigated systematically and discussed with regard to the practical concerns in full-scale settings. The failure envelops of internal liners are found to be within that of the composite layers, which reveals that the liner is the weakest link for composite Riser design. Results show that the composite Risers can be more prone to vortex-induced vibration (VIV) due to their lower structural frequencies. In the present study, the composite Riser yields 25.5% higher RMS strains than the Steel Riser. Placement of buoyancy modules along the Riser may be critical for the design against VIV, and our results show that the modules are not recommended at the top region of the Riser, especially if a top-sheared current is expected. Instead, it is preferable to implement them at the bottom-half portion of the Riser and as a continuously buoyed region rather than short discrete buoys separated with gap spaces. Composite Risers with different metallic liners are studied, and the titanium liner Riser is found to be favourable over the Steel and aluminum liner Risers.
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Global-Local Analysis of a Full-Scale Composite Riser During Vortex-Induced Vibration
Volume 7: CFD and VIV, 2013Co-Authors: Yu Chen, Rajeev K. JaimanAbstract:This paper presents a global-local analysis procedure to demonstrate the feasibility of a composite Riser and its advantages over the traditional Steel counterpart. This procedure starts from the local design of the sandwich tubular structure of Riser section. The equivalent material properties of the sandwich tube are obtained using classic composite theory and they are used to parameterize the full-scale Riser model in global analysis. The global analysis mainly focuses on the vortex-induced vibration (VIV). The methodology is first verified by comparison with experimental data and results produced by SHEAR 7. Four representative cases are then studied and the results show that the critical loads experienced by the composite Riser are much lower than that of the Steel one due to its lightweight. The lightweight composite Riser requires lower top tension and fewer buoyancy cans, which is economically beneficial. The failure envelopes of both composite and Steel Riser sections are obtained by performing damage modelling techniques. The results show that composite Riser yields larger safety margin. Overall, this paper demonstrates that composite Riser is technically feasible and its high performance/weight ratio would make it a promising design for deepwater environment, where self-weight is a big challenge that is hindering the development of traditional Steel Riser.Copyright © 2013 by ASME
Rafael Loureiro Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Parallel Dynamic Optimization of Steel Risers
Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme, 2010Co-Authors: Rafael Loureiro Tanaka, Clóvis De Arruda MartinsAbstract:This paper addresses the use of optimization techniques in the design of a Steel Riser. Two methods are used: the genetic algorithm, which imitates the process of natural selection, and the simulated annealing, which is based on the process of annealing of a metal. Both of them are capable of searching a given solution space for the best feasible Riser configuration according to predefined criteria. Optimization issues are discussed, such as problem codification, parameter selection, definition of objective function, and restrictions. A comparison between the results obtained for economic and structural objective functions is made for a case study. Optimization method parallelization is also addressed.
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Parallel Dynamic Optimization of Steel Risers
Volume 3: Pipeline and Riser Technology; Ocean Space Utilization, 2008Co-Authors: Rafael Loureiro Tanaka, Clóvis De Arruda MartinsAbstract:The design of an ultradeepwater Steel Riser is known to be a challenging task, considering the several environmental load conditions to be simulated and the long time took by each simulation. To aid in this task, optimization algorithms can be used to automate the search for the best design. The problem, however, is very expensive computationally, motivating the implementation and use of a parallel optimization software coupled with a frequency domain dynamic model. This paper deals with the use of two algorithms to optimize a Steel Riser of given inner diameter and material for both pipe and floater: the genetic algorithm and the simulated annealing. The optimizer is left free to vary the length of the segments and the floater diameter, inside user-defined ranges. Each obtained configuration is tested in a set of load cases with different currents, offsets and waves. Optimization times and performance gain with parallelization is addressed for both algorithms.© 2008 ASME
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a genetic algorithm approach to Steel Riser optimization
Volume 1: Offshore Technology; Offshore Wind Energy; Ocean Research Technology; LNG Specialty Symposium, 2006Co-Authors: Rafael Loureiro Tanaka, Clóvis De Arruda MartinsAbstract:It is well known that the Riser system represents an important part of a production unit’s total cost. To ensure economic feasibility it is important to find means to reduce this cost to its minimum. In order to achieve cost reduction and other design improvements, optimization algorithms have been used in several areas with great success. This paper presents the application of such an algorithm, known as Genetic Algorithm, to the optimization of a Steel Riser taking into account material and installation costs. From a given inner diameter and material for both pipe and floater, the optimizer is left free to vary the number of segments as well as the pipe thickness, length and floater diameter for each segment, inside user-defined ranges. Each obtained configuration is tested in a set of load cases with different currents and offsets. Restrictions such as maximum tension, minimum curvature radius and maximum stress are applied to verify the configurations’ feasibility. Only static analysis is performed.Copyright © 2006 by ASME
H. Ohmura - One of the best experts on this subject based on the ideXlab platform.
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Design concept and experiment of ocean nutrient enhancer "TAKUMI"
Oceans '04 MTS IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600), 2004Co-Authors: K. Ouchi, H. OhmuraAbstract:To increase a primary production in the sea, upwelling and discharging a Deep Ocean Water (DOW) which has very rich nutrient salts into the euphotic surface layer has been proposed by many oceanologists as a "fishing ground of artificial DOW upwelling". But, so far, there are no successful means to make it, because of the problems of the large amount of upwelling DOW, the dilution of nutrient salts in the sea, enduring the rough sea condition, the strength of very long Riser pipe for upwelling, etc. The design concept of ocean nutrient enhancer TAKUMI, featuring the density current for avoiding the dilution of nutrient salts, the spar type submersible floating structure for withstanding the rough sea condition, and the design and analysis of Riser pipe for not only in case of rough sea but also in case of the upending which is world first challenge of election of Steel Riser pipe with gravity fall in the subsea, is introduced. Also, about one year continuous running operation of TAKUMI and the investigation results of the water mass discharged from TAKUMI are reported.