Assessing Mechanical Stresses in Dynamic Power Cables for Floating Offshore Wind Farms

Abstract

Floating offshore wind offers a promising potential in the development of renewable energies. One of the key component of offshore wind farms projects is the inter-array power cable. Additionally, the dynamic behavior of floating support under offshore environmental conditions requires dynamic power cable structures which have to withstand both fatigue and extreme loads over its lifetime. Both global and local analyses are required to properly design a dynamic power cable. Indeed, the axial, bending and torsion loads due to environmental conditions (waves and current) and the floating support motion are calculated from a global model by using a dedicated software. Then, the global loading has to be transferred to local sub-models in order to calculate stresses acting on the different components of the power cable. This paper describes a 3D finite elements (FE) model dedicated to a detailed prediction of stresses in an armoured power cable. The loads under extreme environmental conditions are first evaluated from a global analysis. The local model, developed in a commercial FE software, uses periodic boundary conditions to reduce the computational costs and accurately model cables with constant curvatures in space. The model includes contact pressure and friction effects between all cable components, as well as potential lateral contacts between adjacent armour wires, and the radial stiffness of the cable core. The applicative example, focusing on the amour layers, illustrates the potential of the model.

A computationally efficient finite element model for the analysis of the non-linear bending behaviour of a dynamic submarine power cable

“…The elastic behaviour of each components is characterized by a Young modulus and a Poisson's ratio. Since no reference values were provided by the cable supplier, the values listed in Table 2 were obtained from various sources, including material databases and other studies such as [3] and [34]. The structure mesh is generated from a in-house program developed in MATLAB to ensure the mesh periodicity required for the homogenization method, as presented in [38].…”

“…From a mechanical point of view, the cable time response is determined at different sea states. In such an analysis, the cable is described by a numerical beam model subjected to hydrodynamic loads and platform motions, see [2][3][4][5][6]. It is therefore important to provide the stiffness characteristics of the beam to this model.…”

“…However, the model axial length is taken sufficiently large to limit the edge effects generated with the use of rigid-body assumptions for the end cross-sections. In [3] the axial model is reduced to a representative part of the cable corresponding to the armours helix pitch. Each component is modelled with solid elements.…”

“…It has recently been applied to metallic strands in [38,39]. Thus, as in [3,34] the size of the numerical model is reduced to the helical pitch of the internal components using specific periodic boundary conditions. In addition, the numerical model integrates beam elements to reduce the model size.…”

Mechanical behavior of metallic strip flexible pipes during reeling operation

“…With considerable attention has been paid to the security and reliability of flexible structures in the installation and operation phases [15][16][17][18][19], research on their mechanical behavior during early reeling operation rarely shows in the open literature according to our review, although some similar study regarding reel-laying manipulation might provide some references. Szczotka [20] adopted the rigid finite element method to present the static and dynamic response of an offshore pipe reel-laying process.…”