Sensivity Analysis of Tensioned–Leg Mooring Line Under Variations of Water Depth
Keywords:
Mooring line, tensioned-leg, water depth, floating structureAbstract
Floating structures can provide an alternative solution to the developments in the highly populous urban area. The agile mobility and flexible of deployment for a floating solution are considered more effective in the nearshore areas where the conventional piling for construction of a fixed offshore structure is prohibited due to the protection of the diversity of marine lives. However, the sensitivity of its mooring system subjects to variations of water depth is of research interest. This paper discusses a numerical study of a cylindrical floating structure with its single mooring line connected to the seabed in a tensioned condition. The response of floater heave motion and in-line tension of mooring line for water depths of 300 m, 200 m, 100 m and 50 m were investigated. The mooring line is a steel wire rope subjects to the wave-induced motions of the floater. A numerical model of the floater was analyzed in hydrodynamic software, Ansys-Aqwa, under predefined environmental loading conditions to determine the in-line tension of the mooring system and the behaviors of the floater in a time domain. The results indicated that the floater oscillated at a vertical stiffness which magnitude is inversely proportional to the length of mooring lines. The ratio of the maximum in-line tension for mooring line in the 50 m water depth can be up to 1.52 to the original one in the 300 m water depth if the mooring line with an identical diameter is truncated. This study is significant to provide a reference for the mobility and redeployment of floating structures in locations with different water depth.References
Garrett D.L., 1982. Dynamic Analysis of Slender Rods, J. Energy Resour. Technol., 104(4): 302–306.
Ran Z., 2000. Coupled Dynamic Analysis of Floating Structures in Waves and Currents, Doctoral Dissertation, Texas A&M University.
Xiao F. and Yang H.Z., 2014. Probabilistic Assessment of Parametric Instability of A Top Tensioned Riser in Irregular Waves, J. Mar. Sci. Technol., 19(3): 245–256.
Radhakrishnan S., Datla R. and Hires, R.I., 2007. Theoretical and Experimental Analysis of Tethered Buoy Instability in Gravity Waves, Ocean Eng., 34(2): 261–274.
Kang H.-S., Tang C.H.-H., Quen L.K., Steven A. and Yu X., 2016. Prediction on Parametric Resonance of Offshore Crane Cable for Lowering Subsea Structures, 2016 IEEE International Conference on Underwater System Technology: Theory and Applications (USYS), IEEE, Penang, Malaysia, 165–170.
Lucor D. and Triantafyllou M.S., 2008. Parametric Study of A Two Degree-of-Freedom Cylinder Subject to Vortex-Induced Vibrations, J. Fluids Struct., 24(8): 1284–1293.
Lee K.Q., Abu A., Muhamad P., Tan L.K., Kang H.S., Tang H.H. and Toh H.T., 2017. Prediction on the Performance of Helical Strakes Through Fluid-Structure Interaction Simulation, Communications in Computer and Information Science, Springer Verlag, Singapore, 538–547.
Wang Z. and Yang H., 2016. Parametric Instability of A Submerged Floating Pipeline between Two Floating Structures Under Combined Vortex Excitations, Appl. Ocean Res., 59: 265–273.
Yang H., Xiao F. and Xu P., 2013. Parametric Instability Prediction in A Top-Tensioned Riser in Irregular Waves, Ocean Eng., 70: 39–50.
Kang H.-S., Wu Y.-T., Quen L.K., Tang C.H.-H. and Siow C.-L., 2017. Underwater Target Tracking of Offshore Crane System in Subsea Operations, Communications in Computer and Information Science, Springer Verlag, Singapore, 126–137.
Akcabay D.T. and Young Y.L., 2015. Parametric Excitations and Lock-in of Flexible Hydrofoils in Two-Phase Flows, J. Fluids Struct., 57: 344–356.
Yang H. and Xiao F., 2014. Instability Analyses of a Top-Tensioned Riser Under Combined Vortex and Multi-Frequency Parametric Excitations, Ocean Eng., 81: 12–28.
Kim M.H. and Koo W.C., 2005. 2D Fully Nonlinear Numerical Wave Tanks, Numerical Models in Fluid-Structure Interaction, WIT Press, 43–81.
Bae Y.H. and Kim M.-H., 2013. Influence of Failed Blade-Pitch-Control System to FOWT by Aero-Elastic-Control-Floater-Mooring Coupled Dynamic Analysis, Ocean Syst. Eng., 3(4): 295–307.
Kang H.-S., Kim M.-H., Bhat Aramanadka S.S.and Kang H.-Y., 2014. Dynamic Response Control of Top-Tension Risers by A Variable Damping and Stiffness System with Magneto-Rheological Damper, ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering (OMAE), Volume 6A: Pipeline and Riser Technology, San Francisco, California, USA.
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