Riser loads
Visualisation of riser VIV calculation
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.

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 Concept 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 :

The following tools are used to study riser loads :


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:

  • 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)

On The Numerical Prediction Of Transitional Flows With Reynolds-Averaged Navier-Stokes And Scale-Resolving Simulation Models
Pereira, F.S. and Vaz, G., OMAE ASME 35th International Conference on Ocean, Offshore and Arctic Engineering, Busan, South Korea, 2016

An Innovative Oil Pollution Containment Method for Ship Wrecks Proposed for Offshore Well Blow-outs
F. Andritsos (Joint Research Center) and Hans Cozijn (MARIN), OMAE Conference 2011, Rotterdam, 2011

The DIFIS System for Removal of Oil from Shipwrecks Evaluation of Operational Conditions, Survival Conditions and System Deployment
Hans Cozijn (MARIN) and Fivos Andritsos (Joint Research Center), OCEANS'11 Conference, Kona, Hawaii, 2011

Effectiveness of Polyethylene Helical Strakes in Suppressing VIV Responses After Sustaining High Roller Load Deformation During S-lay Installation
Boubenider, R., Alptunaer, K., Fourchy, P. and Wilde, J. de, 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

Most recent riser load articles written for MARIN Report
(complete overview of articles can be found under Publications)

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

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