CFD Simulation of Vortex Induced Vibration for FRP Composite Riser with Different Modeling Methods

Abstract

Featured Application: Three different risers, i.e., conventional steel riser, composite riser with orthogonal reinforcements and tailored composite riser, are compared for their VIV characteristics. The effects of 2D and 3D models and fluid-structure interaction (FSI) have been considered and two different modeling methods are established to simulate the FRP composite risers. This paper will serve to further understand the dynamic characteristics of the FRP composite risers and improve the utilization of the FRP composite risers in real projects. We believe present paper would appeal to the researchers working on the design and analysis of composite structures and their optimizations.Abstract: Steel risers are widely used in offshore oil and gas industry. However, the production capacity and depths are limited due to their extreme weight and poor fatigue and corrosion resistance. Nowadays, it is confirmed that fiber reinforced polymer (FRP) composite risers have apparent advantages over steel risers. However, the study of vortex induced vibration (VIV) for composite risers is rarely involved. Three different risers (one steel riser and two composite risers) were compared for their VIV characteristics. The effects of 2D and 3D models and fluid-structure interaction (FSI) were considered. The models of composite risers are established by effective modulus method (EMM) and layered-structure method (LSM). It is found that 2D model are only suitable for ideal condition, while, for real situation, 3D model with FSI has to be considered. The results show that the displacements of the FRP composite risers are significantly larger than those of the steel riser, while the stresses are reversed. In addition, the distributions of the displacements and stresses depend on the geometries, material properties, top-tension force, constraints, etc. In addition, it is obvious that EMM are suitable to study the global working condition while LSM can be utilized to obtain the results in every single composite layer.

Experimental Study on Vortex-Induced Vibration of Risers Considering the Effects of Different Design Parameters

“…Generally speaking, the VIV responses of the riser in the flow direction and the cross-flow direction (90 • with respect to the flow direction) are obviously different. In flow direction, the displacement is maintained at a relatively stable value, and vibrates slightly after the initial growth [35]. On the other hand, the vibration in the cross-flow direction of the riser is much more significant for the VIV study.…”

Comparative Study of Vortex-Induced Vibration of FRP Composite Risers with Large Length to Diameter Ratio Under Different Environmental Situations

“…For FRP composite risers, ACP (Pre), Static Structural and Modal modules were involved while for steel risers, only Static Structural and Modal modules were required. In order to achieve the VIV simulation in ANSYS Workbench 17.1, the following modules were included: Geometry, ACP (Pre), Transient Structural, Fluid Flow, ACP (Post) and System Coupling [19]. Generally speaking, Geometry was utilized to create the geometries of risers and flow zones; ACP (Pre) and ACP (post) were employed to include the data of materials and lamination information for composite risers (risers 2 and 3) and to show the stress and deformation response of every composite laminae, respectively; Transient Structural was used to simulate the dynamic responses of risers; System Coupling was applied to achieve the data transfer between Transient Structural and Fluid Flow.…”

“…In this study, layered-structure method (LSM) [19] was employed for FRP composite riser simulation and their geometries are listed in Table 4. For the FRP composite risers, the data of material properties, the thicknesses of liner and composite laminate, reinforced fiber angles, the layer numbers of each lamina with different fiber orientations and the laminate stacking sequences were inputted in the module of ACP (Pre) and the stress and deformation response of every composite laminae were obtained in ACP (Post).…”

“…Besides the research of mechanical properties of FRP composite materials in seawater, the responses and performances, including load distributions, fatigue, and vortex-induced vibrations (VIVs) of composite risers under environmental and functional loads have also been investigated [12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The improvement of composite risers in performance over a pure metallic mandrel had been proved through a scaled-down test [23].…”

Maximization of Eigenfrequency Gaps in a Composite Cylindrical Shell Using Genetic Algorithms and Neural Networks

“…In the offshore oil and gas exploitation industry, risers are indispensable components that are vulnerable to vortex-induced vibration. Vortex-induced vibration strictly depends on the natural frequencies of the risers, so there is a need for optimizing the design of fiber reinforced polymer composite risers by considering different laminate stacking sequences and different lamina thicknesses [14,15]. This approach grants the possibility of avoiding resonance if external excitation frequencies are confined to a large interval with finite lower and upper limits [16].…”