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 and density differences. And the displacement and stress in the top region are sensitive to vessel motion.
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., through studies 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 the consensus would appear that the structures are vulnerable to large deformation under the ISW excitation; see Cai et al., (2006); Huang et al., (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 in underwater production systems with the advantages of simplicity in structure, low costs, and no need for top tension compensation. Furthermore, the deformation and stress responses of SCRs subjected to ISWs are the key factors for analyzing the feasibility of its underwater application. Compared with the CFD method, the study on the dynamic responses of such a slender riser is more effective and easier to achieve in the calculation of structural responses by simulating the dynamics of the risers and expressing the fluid force with a numerical scheme.
