General information
The loads on risers between a floater and the seabed or between two floaters are determined by the vessel motions, direct wave loads and current loads. In this type of analysis the riser loads and floater motions need to be assessed in a coupled manner. Global loads and fatigue life of risers are often dominated by Vortex Induced Vibrations (VIV). In currents alternating vortices will develop on the riser which can excite the riser in one or more of its natural frequencies. Resonant type VIV occurs when the vortex shedding frequency gets close to one of the natural frequencies. VIV can be of major concern because of the increase in drag loads and the high fatigue damage means high investment and maintenance costs of the risers.
The loads on risers between a floater and the seabed or between two floaters are determined by the vessel motions, direct wave loads and current loads. In this type of analysis the riser loads and floater motions need to be assessed in a coupled manner. Global loads and fatigue life of risers are often dominated by Vortex Induced Vibrations (VIV). In currents alternating vortices will develop on the riser which can excite the riser in one or more of its natural frequencies. Resonant type VIV occurs when the vortex shedding frequency gets close to one of the natural frequencies. VIV can be of major concern because of the increase in drag loads and the high fatigue damage means high investment and maintenance costs of the risers.
Services & Activities
The Offshore Department has in the last decade put a lot of research effort in riser VIV, as well as VIM for structures such as spars and semi-submersibles. A dedicated test set-up has been built in our High Speed Basin to carry out large scale high Reynolds VIV tests on riser sections. In this manner accurate measurement of lift and drag coefficients can be carried out, as well as flow visualisations and PIV measurements. In the test set-up it is even possible to carry out full-scale measurements on riser sections up to 4 m in length.
The Trials and Monitoring Department is also involved in investigations into riser loads. State-of-the-Art equipment and experience is available for instrumentation and offshore monitoring of riser loads.
The Offshore Department has in the last decade put a lot of research effort in riser VIV, as well as VIM for structures such as spars and semi-submersibles. A dedicated test set-up has been built in our High Speed Basin to carry out large scale high Reynolds VIV tests on riser sections. In this manner accurate measurement of lift and drag coefficients can be carried out, as well as flow visualisations and PIV measurements. In the test set-up it is even possible to carry out full-scale measurements on riser sections up to 4 m in length.
The Trials and Monitoring Department is also involved in investigations into riser loads. State-of-the-Art equipment and experience is available for instrumentation and offshore monitoring of riser loads.
Facilities & Tools
Model tests addressing riser loads are carried out in the following MARIN facilities :
Model tests addressing riser loads are carried out in the following MARIN facilities :
- Offshore Basin: DP model tests in combined current, waves and wind
- Shallow Water Basin
- High Speed Basin: model tests in waves
The following tools are used to study riser loads :
DYNFLOAT: Assessment of dynamic mooring system loads and tanker motions
DYNFLX: Simulation of lines, pipes and flexible risers
DYNFLX: Simulation of lines, pipes and flexible risers
Software Sales
Some software tools are available for commercial use outside MARIN. A complete overview of these software tools for sale can be found under Software Sales.
Some software tools are available for commercial use outside MARIN. A complete overview of these software tools for sale can be found under Software Sales.
Experience
The list below gives a review of riser load projects carried out at MARIN:
The list below gives a review of riser load projects carried out at MARIN:
- GAP model tests (SBM) - 2006
- High Reynolds VIV tests (2H Offshore) -2004
- High Reynolds VIV tests (BP) -2002
- Multi-mode riser VIV tests BT
Most recent riser load papers presented by MARIN
(complete overview of papers can be found under Publications)
(complete overview of papers can be found under Publications)
Effectiveness of Polyethylene Helical Strakes in Suppressing VIV Responses After Sustaining High Roller Load Deformation During S-lay Installation
Rafik Boubenider (Stress Engineering Services; Inc.); Kaya Alptunaer (Eni Petroleum); Paul Fourchy (Murphy Exploration & Product, Offshore Technology Conference (OTC), Houston, 2008
Exploratory Free Standing Riser VIM Model Tests
Jaap de Wilde (MARIN), 3rd International Workshop on Applied Offshore Hydrodynamics (IWAOH), Coppe/UFRJ - LabOceano, Rio de Janeiro, 2007
Model Tests on the Vortex Induced Motions of the Air Can of a Free Standing Riser System in Current
Jaap de Wilde (MARIN), DOT Conference, Stavanger, 2007
Viscous Flow Computations on Smooth Cylinders - a Detailed Numerical Study with Validation
Guilherme Vaz, Remmelt van der Wal (MARIN), Christophe Mabilat and Paul Gallager (ATKINS), OMAE Conference, San Diego, 2007
Experimental investigation into the vortex formation in the wake of an oscillating cylinder using Particle Image Velocimetry
de Wilde, J.J., Huijsmans, R.H.M. and Tukker, J. (MARIN), ISOPE Conference, San Francisco, 2006
Rafik Boubenider (Stress Engineering Services; Inc.); Kaya Alptunaer (Eni Petroleum); Paul Fourchy (Murphy Exploration & Product, Offshore Technology Conference (OTC), Houston, 2008
Exploratory Free Standing Riser VIM Model Tests
Jaap de Wilde (MARIN), 3rd International Workshop on Applied Offshore Hydrodynamics (IWAOH), Coppe/UFRJ - LabOceano, Rio de Janeiro, 2007
Model Tests on the Vortex Induced Motions of the Air Can of a Free Standing Riser System in Current
Jaap de Wilde (MARIN), DOT Conference, Stavanger, 2007
Viscous Flow Computations on Smooth Cylinders - a Detailed Numerical Study with Validation
Guilherme Vaz, Remmelt van der Wal (MARIN), Christophe Mabilat and Paul Gallager (ATKINS), OMAE Conference, San Diego, 2007
Experimental investigation into the vortex formation in the wake of an oscillating cylinder using Particle Image Velocimetry
de Wilde, J.J., Huijsmans, R.H.M. and Tukker, J. (MARIN), ISOPE Conference, San Francisco, 2006
Most recent riser load articles written for MARIN Report
(complete overview of articles can be found under Publications)
(complete overview of articles can be found under Publications)
Model test investigation of flow phenomena around air can assembly for Grouped SLOR concept initiated by Subsea7
Jaap de Wilde, MARIN Report, 2008
Deepwater FPSO for Brazil under scrutiny in MARIN's Offshore Basin
Hans Cozijn & Charlotte Saltner, MARIN Report, 2007
Rising to the challenge as free standing and hybrid risers increase in popularity
Jaap de Wilde, MARIN Report, 2007
Marco Polo JIP generates excellent hurricane data
Radboud van Dijk, MARIN Report, 2006
UMS: MARIN’s special underwater eye
Bas Buchner, MARIN Report, 2006
Jaap de Wilde, MARIN Report, 2008
Deepwater FPSO for Brazil under scrutiny in MARIN's Offshore Basin
Hans Cozijn & Charlotte Saltner, MARIN Report, 2007
Rising to the challenge as free standing and hybrid risers increase in popularity
Jaap de Wilde, MARIN Report, 2007
Marco Polo JIP generates excellent hurricane data
Radboud van Dijk, MARIN Report, 2006
UMS: MARIN’s special underwater eye
Bas Buchner, MARIN Report, 2006
Contact
For more information on how MARIN can help your organisation with the issue of riser loads and VIV, please contact:
For model tests and analysis :Offshore Department
For full scale measurements :Trials and Monitoring Department
For more information on how MARIN can help your organisation with the issue of riser loads and VIV, please contact:
For model tests and analysis :Offshore Department
For full scale measurements :Trials and Monitoring Department