Vortex Induced Vibration and Structural Integrity of Deep Water Flexible Risers

Lead Research Organisation: Imperial College London
Department Name: Dept of Aeronautics


The long flexible slender multi-layered pipes, called unbonded flexible risers, are considered as the new-generation risers for deep water applications. However their complex design and highly non-linear behviour coupled with the fact that they undergo types of extreme loadings which are different to those experienced by conventional rigid risers, currently pose many challenges to the offshore industry. The focus this work is on developing fluid, structural, and coupling models and the numerical procedures for the prediction of dynamic response of flexible risers due to vortex induced vibration, in cases where accurate simulation of their complex non-linear behaviour is a critical step in the analysis. In the structural simulation, it is intended to adopt a multi-scale non-linear finite element procedure which consistently links simulations conducted at a detailed small scale and a large structural scale. The fluid simulation work involves the development of a quasi-three-dimensional fluid code to model the cross flow around the flexible risers. The structural and fluid codes will be coupled together by developing an efficient fluid-solid interaction algorithm. The results from the numerical simulation will be validated against the results of experiments which will also be carried out as part of the project.


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Description The simulations capability we have produced allows us to model very long oil riser pipes that suffer from a fluid structure interaction known as vortex induced vibration (VIV) that can lead to failure of these pipes due to fatigues. The length of these pipes is very long O(1000D) making the simulation of the full problem intractable. Previous approaches have used a series of 2D slices to represent to hydrodynamics which did not fully capture the 3D anisotropic nature of the fluid flow. We have extended this approach to a "thick" strip method which allows us to capture the local anisotropic nature of the fluid flow but also trivially parallelise the approach to be able to model very long pipes in a tractable timescale.
Exploitation Route At a conference in 2015 I discussion with a representative of the US Airforce about using this technique to model the guide strings on parachutes. In a further invitation to the National University of Singapore in January 2017 I discussed the use of the Thick strip method with Professor Rajeev Jaiman who is extending his codes in vortex induced vibration to include this approach. One researcher, Dr Yan Bao, now has an academic position in Shanghai Jaitong University and continues to develop and promote the technology. Finally we are now part of recent EU-Brazil award focusing on wind engineering where the technology is being applied to understand the fluid structure interaction of a turbine blade when it is parked in a stationary position. This grant started in June 2019 and runs until May 2021.
Sectors Aerospace, Defence and Marine,Environment

Description Council of Science and Technology Review on Modelling
Geographic Reach National 
Policy Influence Type Membership of a guideline committee
Description ExaFlow
Amount £254,824 (GBP)
Funding ID 671571 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 11/2015 
End 10/2018
Title Nektar++ version 4.0.1 
Description Nektar++ is a tensor product based finite element package designed to allow one to construct efficient classical low polynomial order h-type solvers (where h is the size of the finite element) as well as higher p-order piecewise polynomial order solvers. 
Type Of Technology Software 
Year Produced 2014 
Open Source License? Yes  
Impact The software is being used by a number of national and international groups and our web site is currently being visited up to 100 times a day according to google analytics 
URL http://www.nektar.info/downloads/file/nektar-source-tar-gz-2/