Marine growth has varied negative effects on offshore structures and is still an engineering challenge during design and maintenance steps. Several standardized inspections methods were thus developed in view to measure useful parameters: percentage of cover, weight and thickness of marine growth. One of the key lock relies on the definition of roughness.
Scientific advances and innovation
Since 20 years, one single definition of roughness due to marine-growth is recommended for hard marine growth. Recent measurements carried out by University of Nantes show high heterogeneity of the size and the density of individuals. Preliminary studies with Total and Ifremer showed an increase of 20% of the loading due to micro-roughness. The innovation relies on the building of a new definition of the roughness that facilitates the relationship with on site measurement with the Aksi-3D device, developed by University of Nantes and MAREI (Ireland).
Expected technical and economic impact
- Improve the modelling of hydrodynamic coefficients for engineers in presence of marine growth
- In view to optimize MRE design and reduce system maintenance costs
- By improving the definition of roughness due to hard marine macro-organisms
Key project milestones
- April 2017 - Project kickoff
- October 2017 - Bibliography synthesis Unifed definition of roughness
- April 2018 - Tests requirements and computation test based
- April 2020 - New definition and model
The objective is to propose a new formulation of the roughness to certification companies for MRE systems to account for their specificities in comparison with Oil and Gaz field. We want to produce a software too for the computation of hydrodynamic coefficients as a function of the roughness and marine environmental conditions.
Publications and papers published
- Schoefs, F., Bakhtiari, A., Hameryoun, H., Quillien, N., Damblans, G., Reynaud, M., Berhault, C., O’Byrne M. “Assessing and modeling the thickness and roughness of marine growth for load computation on mooring lines”, Floating Offshore Wind Turbine conference (FOWT 2019), session Friday Morning ‘Wind Energy Devices I’, 24 – 26 April 2019, Le Corum, Montpellier, France, (2019).
- Bakhtiari, A., Schoefs, F. & Ameryoun, H. “A review of the biofouling parameters influencing the drag force coefficient of offshore structures”. 3rd International Conference on Renewable Energies Offshore (RENEW 2018), session Tuesday Morning ‘Wind Energy Devices I’, 8 pages, 8 – 10 October 2018, IST Congress Centre, Lisbon, Portugal, (2018).
- Bakhtiari A., Schoefs F., Ameryoun H., “Unified Approach For Estimating Of The Drag Coefficient In Offshore Structures In Presence Of Bio-Colonization”, Proc. of 37th int. conf. on Offshore Mechanics and Arctic Engineering, (M.A.E’18), paper 78757, June 17-22, 2018, Madrid, Spain, 7 pages, proc. On CD-Rom (ASME 2018).
- Bakhtiari A., Schoefs F., Berhault C., Ameryoun H., “Evaluation of marine growth parameters effects on offshore structures loading”, paper #29, 54th ESReDA Seminar on Risk, Reliability and Safety of Energy Systems In Coastal and Marine Environments, organized by Université de Nantes, Sea and Litoral research Institute – FR CNRS 3473, MSH Ange Guepin, April 25th – 26th, 2018, Nantes, France (2018).