On the importance of mooring system parametrisation for accurate floating structure designs

• Published in: Marine structures Vol. 72; pp. 102765 - 23
• Main Authors: Barrera, Carlos, Guanche, Raúl, Rodríguez, Álvaro, Armesto, José A., Losada, Iñigo J.
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 01.07.2020; Elsevier BV
• Subjects: Design; Drag; Drag coefficient; Drag coefficients; Experimental; Floating structures; Hydrodynamics; Length; Loads (forces); Mathematical models; Model accuracy; Mooring; Mooring systems; Numerical; Numerical models; Parameterization; Parameters; Sensitivity analysis; Static models; Stiffness; Validation; Variability; Weight; Validation; Numerical; Mooring; Experimental
• ISSN: 0951-8339; 1873-4170
• DOI: 10.1016/j.marstruc.2020.102765

This paper analyses the importance of mooring design parametrisation on the dynamic behaviour of mooring loads. An exhaustive sensitivity analysis is performed to evaluate the variability of mooring loads because of inaccuracies in the definition of model inputs, including physical and numerical parameters. Results show a relevant dependence on the length and significance in other parameters, such as the weight together with the hydrodynamic equivalent diameter and the drag forces. An inaccuracy below 1% in the mooring reference length can generate loads of up to twice the design, and an incorrect definition of the weight or the drag coefficient in the mooring design can lead to a design load variability of up to 30%. Stiffness plays a crucial role in snap events, reaching load differences of 19% depending on the stiffness selected. This research is based on a set of numerical models capable of predicting the mooring system response. A dynamic numerical model with two schemes of resolution is implemented and calibrated according to an experimental test campaign. Other sources of results provided by a quasi-static model and commercial software, Sesam (DNV-GL), are incorporated. In general, the dynamic numerical models show a good accuracy with an experimental database composed by a set of 2D prescribed movement tests at the fairlead of the mooring system. •Importance of the mooring parametrisation to represent its dynamic behaviour accurately.•Design recommendations for each parameter of the mooring system.•Exposure of different numerical schemes to simulate the dynamic behaviour of the mooring system.•Limitations of numerical models in the prediction of loads and movements.