• Title/Summary/Keyword: Riser design

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A Study on the Behavior of Flexible Riser for Upwelling Deep Ocean Water by a Numerical Method (수치해석적 방법을 통한 해양심층수 취수용 유연 라이저의 거동 해석에 관한 연구)

  • JUNG DONG-HO;KIM HYEON-JU;PARK HAN-IL
    • Journal of Ocean Engineering and Technology
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    • v.18 no.4 s.59
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    • pp.15-22
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    • 2004
  • Static and dynamic analyses of a very flexible and light riser, for upwelling the deep ocean water, is performed. In this numerical study, an implicit finite difference algorithm is employed for three-dimensional riser equations. Fluid non-linearity and bending stiffness are considered and solved, using the Newton-Raphson iteration. Maintaining the depth of end point of a flexible and light riser is very important for upwelling deep ocean water in a floating type development system. Weight is attached at the end point of the riser in order to maintain its intake depth. It is designed under the strong surface current and the configuration of the rise is predicted. In the dynamic analysis, the tension variation at the top point of the riser is presented. T e results of this study can contribute to the design of the development system in floating type for upwelling deep ocean water.

Riser Configuration Design for a 15-MW Floating Offshore Wind Turbine Integrated with a Green Hydrogen Facility

  • Sung-Jae Kim;Sung-Ju Park
    • Journal of Ocean Engineering and Technology
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    • v.38 no.3
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    • pp.137-147
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    • 2024
  • Green hydrogen presents a sustainable and environmentally friendly solution for clean energy production and transportation. This study aims to identify the optimal profile of green hydrogen transportation risers originating from a floating offshore wind turbine (FOWT) integrated with a hydrogen production facility. Employing the Cummins equation, a fully coupled dynamic analysis for FOWT with a flexible riser was conducted, with the tower, mooring lines, and risers described using a lumped mass line model. Initially, motion response amplitude operators (RAOs) were compared with openly published results to validate the numerical model for the FOWT. Subsequently, a parametric study was conducted on the length of the buoyancy module section and the upper bare section of the riser by comparing the riser's tension and bending moment. The results indicated that as the length of the buoyancy module increases, the maximum tension of the riser decreases, while it increases with the lengthening of the bare section. Furthermore, shorter buoyancy modules are expected to experience less fatigue damage, with the length of the bare section having a relatively minor impact on this phenomenon. Consequently, to ensure safety under extreme environmental conditions, both the upper bare section and the buoyancy module section should be relatively short.

Comparative Study on Wave Induced Fatigue Analysis Methods for Steel Catenary Riser (파랑하중에 의한 Steel Catenary Riser 피로손상 평가 방법의 비교검토)

  • Lee, Jeong-Dae;Lee, Sung-Je;Jang, Chang-Hwan;Jun, Seock-Hee;Oh, Yeong-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.52 no.3
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    • pp.222-235
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    • 2015
  • The purpose of this study is to suggest guidelines for riser fatigue analysis in terms of selection of reasonable analysis method. Three analysis methods (spectral, regular wave, rain-flow counting) are introduced and compared. As the riser systems give non-linear response, the time-domain analysis method is more preferred than frequency-domain analysis method. The spectral fatigue analysis method, however, is still useful for identifying fatigue prone areas. Once stress RAO is established, fatigue damage can be calculated very quickly. The regular wave method and the rain-flow counting method are more time consuming but give more exact results compare to spectral method. In case of regular wave method, a set of regular waves which represent random sea states is considered for dynamic analysis. The rain-flow counting method is the most intuitive and exact method because it refers time history stresses containing most of non-linear effects of the riser system. However, it is not common for early design stage to use rain-flow counting method because of its high cost. In this study, it was confirmed that the regular wave method is the most cost effective way in specific cases. However, if the system is highly non-linear, it seems that the regular wave method gives less accurate results than rain-flow counting method. Therefore, it is imperative that the engineers select appropriate analysis method based on design stage and given engineering period. This paper also discusses the theoretical background of each calculation method and hydrodynamic aspects of marine riser systems. A steel catenary riser (SCR) line on FPSO was considered and marine dynamic program (OrcaFlex) was used for static and dynamic analysis.

Numerical Study on the Coupled Responses of the Steel Lazy Wave Riser (SLWR) Based on the Basis of Design and Moored FPSO (BoD 기반의 Steel Lazy Wave Riser(SLWR)와 계류된 FPSO와의 연성해석에 관한 수치해석 연구)

  • Kwon, Yong-Ju;Nam, Bo Woo;Park, Byeong-Won;Oh, Seung-Hoon;Jung, Jae-Hwan;Jung, Dongho
    • Journal of Navigation and Port Research
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    • v.43 no.6
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    • pp.344-352
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    • 2019
  • A coupled analysis was performed between the riser to develop oil and gas in ultra-deepwater and the moored floating body. In general, the safety of the riser is conservatively evaluated by considering the maximum offset excluding the coupled analysis with the floating body. In this study, the safety of the riser was analyzed by considering the coupled motion analysis of the moored floating body. The riser is considered steel lazy wave riser (SLWR) applied in the deep sea, and the floating body is determined to FPSO. The methodology was presented on coupled and uncoupled analysis. The coupled effects were analyzed according to the incident wave headings in intact and damaged conditions of mooring lines. The tension of mooring lines, the motion of the floating body, and riser responses were analyzed according to the loading conditions.

Numerical Study on Thermal Characteristics at Absorber Plate of Flat-Plate Solar Collector with Single Riser (평판형 집열기의 단일 지관에서의 입구 Re수에 따른 흡열판 온도분포에 대한수치해석 연구)

  • Kim, Jeong-Bae;Lee, Dong-Won;Baek, Nam-Choon
    • Journal of the Korean Solar Energy Society
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    • v.27 no.3
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    • pp.149-154
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    • 2007
  • It is essential to know the heat transfer characteristics at the absorber plate of Flat-plate solar collector for optimum design. For flat-plate solar collector, it is difficult to experimentally study the effect for the Reynolds number of riser considering low mass flow rate being applied into the collector with one riser tube. So, this study were performed to show the heat transfer characteristics of flat-plate solar collector with single absorber plate and riser for various Reynolds number at riser using commercial code FLUENT 6.0. The base collector size is chosen with $0.4m^2$ as 0.2m by 2m with single riser in this study, Reynolds number at riser is from 200 to 1200 including about 530 at typical flat-plate collector with 10 risers considering the mass flow rate of 0.02kg/s per collector area for the certificate test Through the simulation, the results were presented as the temperature distribution at the absorber plate for various flow rate and solar irradiance conditions, then showed the effective length scale of the absorber plate The real solar irradiation condition is assumed as the constant heat flux condition of $500w/m^2$ considering the annual average solar irradiance in Korea.

A Comparative Study of Approximation Techniques on Design Optimization of a FPSO Riser Support Structure (FPSO Riser 지지구조의 설계최적화에 대한 근사화 기법의 비교 연구)

  • Shim, Chun-Sik;Song, Chang-Yong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.5
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    • pp.543-551
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    • 2011
  • The paper deals with the comparative study of design optimization based on various approximation techniques in strength design of riser support structure installed on floating production storage and offloading unit(FPSO) using offshore operation loading conditions. The design optimization problem is formulated such that structural member sizing variables are determined by minimizing the weight of riser support structure subject to the constraints of structural strength in terms of loading conditions. The approximation techniques used in the comparative study are response surface method based sequential approximate optimization(RBSAO), Kriging based sequential approximate optimization(KBSAO), and the enhanced moving least squares method(MLSM) based approximate optimization such as CF(constraint feasible)-MLSM and Post-MLSM. Commercial process integration and design optimization(PIDO) tools are employed for the applications of RBSAO and KBSAO. The enhanced MLSM based approximate optimization techniques are newly developed to ensure the constraint feasibility. In the context of numerical performances such as design solution and computational cost, the solution results from approximate techniques based design optimization are compared to actual non-approximate design optimization.

Semisubmersible platforms with Steel Catenary Risers for Western Australia and Gulf of Mexico

  • Zou, Jun
    • Ocean Systems Engineering
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    • v.2 no.2
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    • pp.99-113
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    • 2012
  • Steel Catenary Risers (SCR) are the simplest and often the most economic solution compared to other riser types such as flexible pipe, riser towers, top tensioned risers, etc. The top of a SCR is connected to the host platform riser porch. The other end of the SCR connects to flowlines from subsea wells. The riser touchdown point (TDP), which is the location along the riser where contact with the sea floor first occurs, exhibits complex behaviors and often results in compression and fatigue related issues. Heave dynamic responses of semisubmersibles in extreme and operating sea states are crucial for feasibility of SCR application. Recent full field measurement results of a deep draft semisubmersible in Hurricane Gustav displayed the considerable discrepancies in heave responses characteristics between the measured and the simulated results. The adequacy and accuracy of the simulated results from recognized commercial software should be examined. This finding raised the awareness of shortcomings of current commercial software and potential risk in mega investment loss and environmental pollutions due to SCR failures. One main objective of this paper is to attempt to assess the importance and necessity of accounting for viscous effects during design and analysis by employing indicator of viscous parameter. Since viscous effects increase with nearly third power of significant wave height, thus newly increased metocean criteria per API in central Gulf of Mexico (GoM) and even more severe environmental conditions in Western Australia (WA) call for fundamental enhancements of the existing analysis tools to ensure reliable and robust design. Furthermore, another aim of this paper is to address the impacts of metocean criteria and design philosophy on semisubmersible hull sizing in WA and GoM.

Solidifications Simulation of Gray Iron Sheave Product with Consideration of Graphite Precipitation (흑연정출을 고려한 회주철제 시브제품의 응고해석)

  • Ryu, Seong-Gon
    • Korean Journal of Materials Research
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    • v.9 no.2
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    • pp.139-143
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    • 1999
  • Solidification simulation of gray cast iron sheave product was conducted with the consideration of graphite precipitation during solidification, and of casting processes such as post-inoculation method, treatment and rate, the result of which was aimed to be adopted in the field. In risering design(I), shrinkage cavities were predicted to occur in the part below the risers and center part of the product. While the former defect was considered to be due to the solidification behaviour of riser neck, the latter was due to the feeding channel. In design(II), the length of the riser neck was reduced and one top open riser was attached in the center of the product to prevent the formation of shrinkage cavities, whereby defect-free product was produced.

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A comparison of coupled and uncoupled dynamic analysis for the flexible riser in shallow water

  • Jo, Chul-Hee;Kim, Do-Youb;Hwang, Su-Jin;Rho, Yu-Ho
    • Journal of Advanced Marine Engineering and Technology
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    • v.38 no.2
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    • pp.195-201
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    • 2014
  • Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system.

A Comparison of Dynamic Analysis for the Flexible Riser in Shallow Water (천해에서 유연라이저의 동적해석 결과 비교)

  • Jo, Chul-Hee;Kim, Do-Youb;Rho, Yu-Ho;Kim, In-Ho
    • Journal of Coastal Disaster Prevention
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    • v.1 no.4
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    • pp.149-155
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    • 2014
  • Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system.