Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Dynamic responses of a deep-water steel catenary riser subjected to internal solitary waves
Fuheng Li; Haiyan Guo*; Xiaomin Li; Honglu Gu
Engineering College, Ocean University of China
Qingdao, Shandong Province, China

responses of such a slender riser is more effective and easier to achievein the calculation of structural responses by simulating the dynamics ofthe risers and expressing the fluid force with a numerical scheme.

ABSTRACT
Strong shear flows can be induced by the internal solitary wave (ISW),
which plays a considerable role in the dynamic responses of steel
catenary risers (SCRs). A three-dimensional program of SCRs is
established using the slender rod theory. ISW effects are simulated by
the extended Korteweg–deVries theory. The numerical simulation of
the riser’s deformation and stress responses is performed under the ISW,
also considering the coupling effect of vessel motion. The responses
along the riser increase with increasing the interface depth ratios anddensity differences. And the displacement and stress in the top region
are sensitive to vessel motion.

Fig. 1. Diagram of internal solitary wave
(from https://www.zhihu.com/question/271550823/answer/1518450473).
Guo et al., (2013) adopted the finite element method to conduct thedynamic responses of SCRs subjected to the ISW effects. Lou et al.,(2015; 2018) analyzed the effects of internal wave amplitudes on theSCRs by using the virtual work principle. The structural responses ofSCRs under the influence of ISW excitation were determined byGudmestad et al., (2018) using the lumped mass method. As far as theauthors know, the dynamic responses of the SCRs, particularly for thedeformation and stress, have scarcely been investigated detailedly inthe above literature. Moreover, the effects of some key parameters ofISW excitation, such as interface depth ratio and density differences,also need to be further studied systematically. In view of thesignificance of the ISW excitation on SCRs, it is necessary to establish
a reasonable numerical scheme of a SCR and investigate the risers’
deformation and stress induced by ISW effects.
The finite element method has significant advantages in handlingcomplex configurations and boundary conditions. The slender rod
theory is based on the absolute coordinate system and obviates a timeconsuming transformation from a local coordinate to a global
coordinate (Garrett, 1982; Paulling and Webster, 1986), that is essential
in the traditional finite element method. Evidence has shown that thestatic and dynamic behaviors of risers can be reasonably simulatedusing this method (Yang et al., 2012; Ruan et al., 2014). The innovationof this paper is to study the dynamic response properties of steel
catenary risers with large deformation characteristics under internal
wave excitation. And the objective is to investigate the dynamic
responses of a SCR subjected to ISW interface depth ratio and density

KEY WORDS
Internal solitary waves; steel catenary riser; slender rod theory;
deformation; stress.

INTRODUCTION
Internal solitary waves (ISW) exist in two fluid layers with different
densities, as shown in Fig. 1. And a large amount of water energy
converges and diverges violently, resulting in a strong shear flow
during the ISW propagation process, which seriously excites the large
deformation of the riser and threatens its safe operation, i.e., throughstudies by Osborne and Burch, (1980); Cai et al., (2003); Li and Farmer,(2011). Both the Liuhua 11-1 and Lufeng 22-1 oil fields in the South
China Sea have been triggered rupture of their risers by ISW excitation.
Thus, numerous publications on the piles and cylinders on a small scale
subjected to ISW effects can be found in scientific literature, and theconsensus would appear that the structures are vulnerable to large
deformation under the ISW excitation; see Cai et al., (2006); Huang etal., (2013); Wang et al., (2018); Wang et al., (2018); Zhang et al.,(2013); Fan et al., (2017); Cheng et al., (2020).
However, as crude oil and natural gas exploration activities further
extend to deeper waters, steel catenary risers (SCRs) are widely used inunderwater production systems with the advantages of simplicity instructure, low costs, and no need for top tension compensation.
Furthermore, the deformation and stress responses of SCRs subjected toISWs are the key factors for analyzing the feasibility of its underwater
application. Compared with the CFD method, the study on the dynamic

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