Towards the Numerical Modelling of Floating Offshore Renewables
Two finite element models are coupled, with the aim of computing the mutual interactions between fluids and floating solids. The fluid and solid domains are discretised differently in space and time, and at every time step, the solid mesh is mapped onto t
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Abstract Two finite element models are coupled, with the aim of computing the mutual interactions between fluids and floating solids. The fluid and solid domains are discretised differently in space and time, and at every time step, the solid mesh is mapped onto the fluid mesh. The effect of the solid on the fluid dynamics, and vice versa, is modelled through a volumetric penalty force added to the momentum balances of the fluids and solids. A novel algorithm ensures that the action-reaction principle is satisfied at the discrete level. The coupled models are used to simulate uniform flow past a wind turbine, which is represented as a fixed actuator disc. Preliminary results on a floating pile also demonstrate the applicability of the models to fully coupled simulation of a floating spar. This work is a first-step towards the fully coupled modelling of floating wind turbines.
Keywords Fluid-structure interactions Immersed-body approach Finite element method Actuator disc Floating pile Floating wind turbines
1 Introduction The numerical modelling of fluid–structure interactions is important in the context of offshore renewables. This work targets floating wind turbines, where the turbine is supported by a floating pile moored to the seabed. Such devices are attractive in A. Viré (&) J. Xiang M. D. Piggott J-P. Latham C. C. Pain Department of Earth Science and Engineering, Imperial College London, SW7 2AZ London, UK e-mail: [email protected] M. D. Piggott Grantham Institute for Climate Change, Imperial College London, SW7 2AZ London, UK C. J. Cotter Department of Aeronautics, Imperial College London, SW7 2AZ London, UK
Y. Zhou et al. (eds.), Fluid-Structure-Sound Interactions and Control, Lecture Notes in Mechanical Engineering, DOI: 10.1007/978-3-642-40371-2_59, Ó Springer-Verlag Berlin Heidelberg 2014
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deep seas (typically deeper than 50 m), where bottom-mounted foundations are too expensive. The numerical modelling of floating wind turbines is very challenging because of the dynamic interaction between the moving air–water and fluid–solid interfaces, and the presence of both rigid (i.e. the wind turbine) and deformable (i.e. the moorings) solids. Computer models are, however, attractive in studying such coupled fluid–solid problems, because they can analyse different configurations while limiting expensive laboratory or onsite testing. In this work, two finite element models are coupled in order to represent the mutual interactions between fluids and floating solids. The use of separate models, based on different spatial and temporal discretisations, allows for the mesh resolution to be tailored to the specific needs of the fluids and solids, respectively.
2 Numerical Models Consider a solid Vs immersed in a fluid domain Vf. In this work, the interactions between fluids and solids are modelled by filling the regions covered by solids with the surrounding fluid and relaxing the flow to the behaviour of the solids in those regions. The Navier–Stokes equations de
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