Presentation pdf 5.6MB

Coupled mooring analysis of a floating wave energy converter using the Overset framework

The nonlinear interaction between waves and floating wave energy converters (WECs) has become in the recent years one of the biggest challenges for wave power industry. Large displacements of real structures demand accurate and robust numerical tools to solve the problems more efficiently. However, all this nonlinear interactions between the floating structures and the waves result in high computational costs. Movable structures like WECs, floating offshore wind turbines (FOWT), moored ships and floating platforms have been widely analysed by means of numerical models, such as OpenFOAM [1].

The aim of this work is to present a exhaustive analysis of the behaviour of moored floating objects under severe conditions. Previous techniques, such as deforming grid approaches, have problems to handle the large body motions. Therefore, we analyse the performance of the Overset Mesh Library [1] applied to a floating wave energy converter [2]. Numerical results will be compared with experimental data for validation and discussed. The mooring restraints will be computed by means of the MooDy Library [3]. To deal with the over production of turbulence levels, a stabilized turbulence model by Larsen & Fuhrman [6] has been included in the model. The latest updates of IHFOAM [4, 5] are also included.

References [1] ESI-Group, Openfoam the open source cfd toolbox. URL https://www.openfoam.com/ [2] J. Palm, C. Eskilsson, G. M. Paredes, L. Bergdahl. Coupled mooring analysis for floating wave energy converters using CFD: Formulation and validation. International Journal of Marine Energy, ISSN: 2214-1669, Vol: 16, Page: 83-99. [3] J. Palm, C. Eskilsson, L. Bergdahl. An hp-adaptive discontinuous Galerkin method for modelling snap loads in mooring cables. Ocean Engineering, 144:266-276, 2017. [4] P. Higuera, J. L. Lara, I. J. Losada, Realistic wave generation and active wave absorption for Navier-Stokes models: Application to OpenFOAM, Coastal Engineering 71 (2013) 102–118. [5] Di Paolo, B., Lara, J.L., Barajas, G., Paci, A. and Losada, I.J., 2018, June. Numerical analysis of wave and current interaction with moored floating bodies using overset method. In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering (pp. V002T08A037-V002T08A037). American Society of Mechanical Engineers. [6] B. E. Larsen, D. R. Fuhrman, On the over-production of turbulence beneath surface waves in Reynolds-Averaged Navier-Stokes models, Journal of Fluid Mechanics 853 (2018) 419– 460.