Chi Zhang1, Allan R. Magee1, Nuno Fonseca2, Nianxin Ren1, Miguel Rodrigues2, Øyvind Hellan2, and Kok Keng Ang1
1Centre for Offshore Research & Engineering, Department of Civil and Environmental Engineering, National University of Singapore, Singapore 117577
2SINTEF Ocean AS, Trondheim, Norway
Abstract – An innovative floating hydrocarbon storage facility (FHSF) has been proposed to utilize the shielded near-shore area for countries with large demand on the land space such as Singapore and Japan. The concept comprises 14 floating hydrocarbon storage tanks (FHST) and several surrounding floating barges. All the modular designed FHSTs are loosely connected to the barges through soft mooring system so as to reduce the loads, and the entire system will be free floating vertically to reduce the tidal influence. The single FSHT has been proven to have moderate hydrodynamic responses in previous studies, but there still exist concerns on the influence of potential resonance in the narrow gaps and the strong hydrodynamic interactions. The loads on the specially designed soft mooring system have to be checked. The complete system is complex and difficult to analyze. So, experimental studies on a simplified system with two FHST and a surrounding floating barge frame were performed in the ocean basin in SINTEF Ocean. This paper will focus on this simplified system that represents the complete system’s behavior. A series of random, wide-band and realistic random wave tests were carried out to generate benchmark data to verify numerical analysis tools. Subsequently, a hybrid frequency domain and time domain numerical model of the system was established based on potential theory. Empirical coefficients were used to account for viscous damping. Both the numerical and experimental results showed that the hydrodynamic responses of the FHSTs and the loads on the soft mooring system were within the acceptable range even with the hydrodynamic interactions. However, gap resonances were found to be serious due partially to the large motions of the floating barge frame.
Keywords – Hydrodynamic interactions, Gap resonance, VLFS, Floating structures, Hydrocarbon storage.
Mr. Zhang Chi is currently a PhD candidate in the Department of Civil and Environmental Engineering, National University of Singapore. He graduated from Wuhan University of Technology, China with both Bachelor and Master of Naval Architecture and Ocean Engineering degrees. His research mainly focuses on the wave-structure interaction of multi-module large floating structures, hydroelastic response of ship structures, and global strength & fatigue strength of ship structures.