An accurate and computationally efficient small-scale nonlinear FEA of flexible risers

Abstract

a b s t r a c tThis paper presents a highly efficient small-scale, detailed finite-element modelling method for flexible risers which can be effectively implemented in a fully-nested (FE 2 ) multiscale analysis based on computational homogenisation. By exploiting cyclic symmetry and applying periodic boundary conditions, only a small fraction of a flexible pipe is used for a detailed nonlinear finite-element analysis at the small scale. In this model, using three-dimensional elements, all layer components are individually modelled and a surface-to-surface frictional contact model is used to simulate their interaction. The approach is applied on a 5-layered pipe made of inner, outer and intermediate polymer layers and two intermediate armour layers, each made of 40 steel tendons. The capability of the method in capturing the detailed nonlinear effects and the great advantage in terms of significant CPU time saving are demonstrated by comparing the results obtained on elements of pipe of different lengths, equal to one pitch length L p as

Computational homogenization method for the bending analysis of submarine power cables

“…Fig. 2 Correspondence between a pair of nodes L n and R n on the two end-cross sections and the dummy projected node P n , which is constrained to the reference node P R [11] Fig. 3 Cross section of the SPC Fig.…”

“…An alternative is to apply the periodic boundary conditions by taking advantage of the helical symmetry of helical wires thanks to the computational homogenization [8]. This method was early developed to tackle the problem for composite structures [9] and are gradually extended to other structures such as helical ropes [10] and flexible pipes [11].…”

Curvature effect on wet collapse behaviours of flexible risers subjected to hydro-static pressure

“…As the key device for transporting hydrocarbon product from sub-sea reservoirs to floating vessels, flexible risers therefore have to withstand huge hydrostatic pressure without collapse. Flexible riser are multilayered tubular structures which consist of helical wound metallic strips and tapes, and extruded polymeric layers (Rahmati et al 2016), as shown in Figure 1 (National Oilwell Varco 2014). The carcass and the pressure armour are two self-interlocking layers wound by metal strips with constant pitches, which take external and internal pressure, separately.…”