• Title/Summary/Keyword: Flexible riser

Search Result 24, Processing Time 0.022 seconds

Preliminary optimal configuration on free standing hybrid riser

  • Kim, Kyoung-Su;Choi, Han-Suk;Kim, Kyung Sung
    • International Journal of Naval Architecture and Ocean Engineering
    • /
    • v.10 no.3
    • /
    • pp.250-258
    • /
    • 2018
  • Free Standing Hybrid Riser (FSHR) is comprised of vertical steel risers and Flexible Jumpers (FJ). They are jointly connected to a submerged Buoyancy Can (BC). There are several factors that have influence on the behavior of FSHR such as the span distance between an offshore platform and a foundation, BC up-lift force, BC submerged location and FJ length. An optimization method through a parametric study is presented. Firstly, descriptions for the overall arrangement and characteristics of FSHR are introduced. Secondly, a flowchart for optimization of FSHR is suggested. Following that, it is described how to select reasonable ranges for a parametric study and determine each of optimal configuration options. Lastly, numerical analysis based on this procedure is performed through a case study. In conclusion, the relation among those parameters is analyzed and non-dimensional parametric ranges on optimal arrangements are suggested. Additionally, strength analysis is performed with variation in the configuration.

NUMERICAL STUDY OF VORTES-INDUCED VIBRATION FLEXIBLE RISER AND PIPE MODELS (해저석유 생산용 라이저 모형에 대한 Vortex-Induced Vibration 수치계산)

  • Chen, Z.S.;Kim, W.J.;Yoo, J.H.
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2010.05a
    • /
    • pp.295-304
    • /
    • 2010
  • The paper summarizes the VIV-related research with the focus on flexible riser and pipe models subject to various engineering conditions. First of all, a series of numerical simulations for the purpose of validating the efficiency of FSI solution approach (ANSYS MFX) has been performed. The comparison between the simulation and the experimental data shows that the present FSI solution method is capable of giving acceptable estimation to VIV problems. As a meaningful application to engineering problems, some tentative simulation cases which are difficult to carry out in experiment, such as a flexible pipe with internal flow and multi-assembled pipes, have been successfully carried out. The coupling mechanism between vortex shedding and the VIV has been well interpreted.

  • PDF

Sensitivity Study on SCR Design for Spread-Moored FPSO in West Africa

  • Yoo, Kwang-Kyu;Joo, Youngseok
    • Journal of Ocean Engineering and Technology
    • /
    • v.31 no.2
    • /
    • pp.111-120
    • /
    • 2017
  • It is generally acknowledged that the Steel Catenary Riser (SCR) is the most cost-effective riser type for deep-water offshore fields among various risers, including the SCR, flexible riser, and hybrid riser. However, in West Africa, the SCR type may not be suitable for FPSO systems because the large vertical motion of the floater brings about a considerable riser dynamic response. In this paper, an SCR system is designed for the FPSO in the West African field, where the use of a hybrid riser has been preferred. The proposed SCR configuration fulfills the design criteria of the API, such as the strength check and fatigue life. Moreover, a sensitivity analysis is also carried out to improve the certainty in the SCR design of a deep-water FPSO. The parameters affecting the strength and fatigue performance of the SCR are considered.

Arrangement Plan of Buoyancy Modules for the Stable Operation of the Flexible Riser in a Deep-Seabed Mining System (심해저 채광 시스템에서 유연관의 안정적인 운용을 위한 부력재 배치 설계)

  • Oh, Jae-Won;Min, Cheon-Hong;Lee, Chang-Ho;Hong, Sup;Bae, Dae-Sung;Lim, Jun-Hyun;Kim, Hyung-Woo
    • Ocean and Polar Research
    • /
    • v.37 no.2
    • /
    • pp.119-125
    • /
    • 2015
  • This paper focuses on the efficient arrangement plan of buoyancy modules, which plan is used to secure the safe operation and structural stability of a marine riser. The marine riser is connected between a vessel and seabed devices. The movement of the vessel and the seabed devices are affected by the motion of the riser. The riser of a deep-seabed integrated mining system exerts a strong influence on the healthy transfer of minerals. So, buoyancy modules must be equipped to compensate for the problem which is the structure stability and the dynamic motion. Installation locations and quantities of the buoyancy modules are determined by real sea experiments. But this is not easy to do because in real sea experimental conditions the cost is expensive as well as being, time-consuming and dangerous. Therefore, the locations and quantities should be determined by numerical simulation. This method is called simulation-based design. The dynamic analysis models of the riser and the buoyancy modules are built into the commercial software of DAFUL.

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
    • /
    • v.38 no.3
    • /
    • pp.137-147
    • /
    • 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.

Global stabilization of three-dimensional flexible marine risers by boundary control

  • Do, K.D.
    • Ocean Systems Engineering
    • /
    • v.1 no.2
    • /
    • pp.171-194
    • /
    • 2011
  • A method to design a boundary controller for global stabilization of three-dimensional nonlinear dynamics of flexible marine risers is presented in this paper. Equations of motion of the risers are first developed in a vector form. The boundary controller at the top end of the risers is then designed based on Lyapunov's direct method. Proof of existence and uniqueness of the solutions of the closed loop control system is carried out by using the Galerkin approximation method. It is shown that when there are no environmental disturbances, the proposed boundary controller is able to force the riser to be globally exponentially stable at its equilibrium position. When there are environmental disturbances, the riser is stabilized in the neighborhood of its equilibrium position by the proposed boundary controller.

Experimental Study on Elastic Response of Circular Cross-section Slender Body to Forced Oscillation, Waves, and Current (복합 외력환경 중 원형 단면 세장체의 탄성응답에 관한 실험적 연구)

  • Park, Ji-won;Lee, Seung-Jae;Jo, Hyo-Jae;Hwang, Jae-Hyuk;Han, Sung-Hoon
    • Journal of Ocean Engineering and Technology
    • /
    • v.30 no.2
    • /
    • pp.91-99
    • /
    • 2016
  • The global demand for oil and natural gas has increased, and resource development is moving to the deep sea. Floating and flexible offshore structures such as semi-submersible, spar, and FPSO structures have been widely used. The major equipment of floating structures is always exposed to waves, currents, and other marine environmental factors, which cause structural damage. Moreover, flexible risers are susceptible to an exciting force due to the motion of the floating body. The inline and transverse responses from the three-dimensional behavior of a floating structure occur because of various forces. Typical risers are made of steel pipe and applied in the oil and gas development field, but flexible materials such as polyethylene are suitable for OTEC risers. Consequently, the optimal design of a flexible offshore plant requires a dynamic behavior analysis of slender bodies made of the different materials commonly used for offshore flexible risers. In this study, a three-dimensional motion measurement device was used to analyze the displacements of riser models induced by external force factors, and forced oscillation of a riser was linked to forced oscillation under a steady flow and regular wave condition.

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

  • Zou, Jun
    • Ocean Systems Engineering
    • /
    • v.2 no.2
    • /
    • pp.99-113
    • /
    • 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.

Numerical Study on Estimation of Static Configuration of Steel Lazy Wave Riser Using Dynamic Relaxation Method (동적이완법을 이용한 Steel Lazy Wave Riser의 정적형상 추정에 관한 수치해석적 연구)

  • Oh, Seunghoon;Jung, Jae-Hwan;Park, Byeongwon;Kwon, Yong-Ju;Jung, Dongho
    • Journal of Ocean Engineering and Technology
    • /
    • v.32 no.6
    • /
    • pp.466-473
    • /
    • 2018
  • This paper presents an estimation method for the static configuration of a steel lazy wave riser (SLWR) using the dynamic relaxation method applied to estimate the configuration of structures with strong geometric non-linearity. The lumped mass model is introduced to reflect the flexible structural characteristics of the riser. In the lumped mass model, the tensions, shear forces, buoyancy, self-weights, and seabed reaction forces at nodal points are considered in order to find the static configuration of the SLWR. The dynamic relaxation method using a viscous damping formulation is applied to the static configuration analysis. Fictitious masses are defined at nodal points using the sum of the largest direct stiffness values of nodal points to ensure the numerical stability. Various case studies were performed according to the bending stiffness and size of the buoyancy module using the dynamic relaxation method. OrcaFlex was employed to validate the accuracy of the developed numerical method.

Significance of seabed interaction on fatigue assessment of steel catenary risers in the touchdown zone

  • Elosta, Hany;Huang, Shan;Incecik, Atilla
    • Structural Engineering and Mechanics
    • /
    • v.57 no.3
    • /
    • pp.403-423
    • /
    • 2016
  • The challenges involved with fatigue damage assessment of steel catenary riser (SCR) in the touchdown zone (TDZ) are primarily due to the non-linear behaviour of the SCR-seabed interaction, considerable uncertainty in SCR-seabed interaction modelling and geotechnical parameters. The issue of fatigue damage induced by the cyclic movements of the SCR with the seabed has acquired prominence with the touch down point (TDP) interaction in the TDZ. Therefore, the SCR-seabed response is critical for reliable estimation of fatigue life in the TDZ. Various design approaches pertaining to the lateral pipe-soil resistance model are discussed. These techniques have been applied in the finite element model that can be used to analyse the lateral SCR-seabed interaction under hydrodynamic loading. This study investigates the sensitivity of fatigue performance to geotechnical parameters through a parametric study. In this study, global analyses are performed to assess the influence of vertical linear seabed springs, the lateral seabed model and the non-linear seabed model, including trench evolution into seabed, seabed normalised stiffness, re-penetration offset parameter and soil suction resistance ratio, on the fatigue life of SCRs in the TDZ.