Effects of Different Design Parameters on the Vortex Induced Vibration of FRP Composite Risers Using Grey Relational Analysis

Abstract

Risers are indispensable components of offshore platform systems that connect the wellhead at the sea bottom and to the platform at the sea surface and are normally made of high grade steel. Nowadays, fiber reinforced polymer (FRP) composite has been recognized as an attractive alternative riser material. Similarly to steel risers, FRP composite risers are also vulnerable to vortex induced vibration (VIV), and the effects of the composite makeup of these risers on VIV are the subject of the present investigation. Three risers (the tailored design composite riser, the composite riser with orthogonal reinforcements and the steel riser), three current velocities (0.36 m/s, 1.22 m/s and 2.13 m/s) and three water depths (12.5 m, 25 m and 37.5 m) are considered. In total, 9 study cases using orthogonal array (OA) sampling are investigated to study the risers’ VIV characteristics. The computational fluid dynamics (CFD) simulations with coupled fluid–structure interaction (FSI) are used to obtain the risers’ natural frequencies, global displacements, global stresses and the stress distributions in each composite lamina. The effect of 5 parameters (Etension, Ebending, L/Douter, tension force and current velocity) on the VIV amplitude in a cross flow direction of the risers is analyzed using Grey relational analysis (GRA) and the Grey relational grade of these parameters are: r 05 ( Velocity ) > r 03 ( L / D outer ) > r 04 ( Tension Force ) > r 01 ( E t e n s i o n ) > r 02 ( E b e n d i n g ) .

Review of Composite Marine Risers for Deep-Water Applications: Design, Development and Mechanics

“…The fundamental frequency of VIV in composite risers was discovered to be less due to its comparative lower mass, but that its worth was relatively insignificant [98][99][100][101][102][103][104]. This behaviour was confirmed in some recent studies [143][144][145][146] showing that the fundamental frequency of VIV in composite risers was lower due to the stiffness property of a composite riser because the composite riser was sensitive to structural damping and tension fluctuations. Generally, the VIV could be reduced by increasing tension and damping in the composite riser.…”

“…In addition to studying the mechanical properties of composite materials in sea water, there are effects from fatigue, load distributions, global responses and performances of the full-length composite riser. However, the CPR tube, its stress joint, steel tension joint and other standard joints face global functional and environmental conditions [98,[143][144][145][146]266]. The effects of functional loadings have also been studied in comparative studies presented on both steel and composite risers, including vortex-induced vibrations (VIVs) and resonances on the CPR [11,55,[199][200][201][202]246].…”

“…The vorticity profiles are shown in Figure 18. The natural frequencies and reduced velocities of nine cases were investigated and further examined in [144][145][146], who presented mode shapes for the FRP composite risers with distinctively different responses to those of steel risers. The study concluded that at 2.13 m/s, the VIV responses of all three risers were almost 30 times those at 0.36 m/s and 3 times those at 1.22 m/s.…”

“…This has also led to advances in the use of TCP pipes on composite risers and related marine composite tubulars for water injection, transport, product transfer and loading and fluid discharge services [31,51,150]. Based on numerical models presented on different CPR models of well-validated composite risers with safety profiles from results of the stress analysis, conducted in ANSYS APDL [137][138][139][140][141][142] and ANSYS ACP [143][144][145][146][149][150][151][152], respectively. Additionally, both researchers used different platforms-while the former used a TLP (tension leg platform), the later used a SPAR (single-point anchor reservoir) and a PCSemi (paired-column semisubmersible).…”

Prediction of the Deterioration of FRP Composite Properties Induced by Marine Environments

“…The use of fiber-reinforced polymer (FRP) composites is becoming increasingly accepted in almost every industry sector, either for entire structures [1,2] or in combination with other, so-called traditional materials [3][4][5]. The marine industry sector is no exception to this trend [6], as FRP composites are finding application in the transportation industry, especially in the maritime sector, whether it be in the construction of lightweight ship structures [7,8] or other marine structures [9,10].…”