Various hydrodynamic maneuvering models are available for modeling the slow motion horizontal plane dynamics of mooring and towing systems. In previous work, we compared four representative and widely used maneuvering models and assessed them based on the design methodology for mooring systems developed at the University of Michigan. In this paper, we study the impact of experimental uncertainties in the maneuvering coefficients on mooring system dynamic analysis. Uncertainties in higher order coefficients may even result in sign change as measured by different experimental facilities. This may indicate lack of robustness in maneuvering modeling. In our recent work, maneuvering models were classified in two schools of thought, each having a different set of coefficients subject to uncertainties. The first school is represented by the Abkowitz (A-M) and the Takashina (T-M) models, and the second by the Obokata (O-M) and the Short Wing (SW-M) models. The design methodology developed at the University of Michigan uses time independent global properties of mooring system dynamics to compare the maneuvering models, and assess their sensitivity and robustness. Equilibria, bifurcation sequences and associated morphogeneses, singularities of bifurcations, and secondary equilibrium paths are such global properties. Systematic change of important coefficients in each model shows that, for both schools of thought, sensitivity to first order terms is high while sensitivity to higher order terms is low. Accuracy in measurement of first order terms is high while accuracy in measurement of higher order terms is low. These two tendencies reduce each other’s impact, providing acceptable robustness.
Sensitivity and Robustness of Hydrodynamic Mooring Models
Contributed by the OOAE Division of the American Society of Mechanical Engineers for publication in the ASME JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received by the ASME OOAE Division, October 2001; final revision, January 2002. Guest Associate Editor: A. Fernandes.
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Matsuura, J. P. J., Bernitsas, M. M., Garza-Rios, L. O., and Nishimoto, K. (October 22, 2002). "Sensitivity and Robustness of Hydrodynamic Mooring Models ." ASME. J. Offshore Mech. Arct. Eng. November 2002; 124(4): 179–189. https://doi.org/10.1115/1.1510873
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