Some uncertainties associated with wind and wave description and their importance for engineering applications

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Some uncertainties associated with wind and wave description and their importance for engineering applications

Bitner-Gregersen, Elzbieta M. / Ewans, Kevin C. / Johnson, Michael C.

In the context of the joint ISSC-ITTC UMSOS (Uncertainty Modelling for Ships and Offshore Structures) Workshop some uncertainties of wind and wave data and models are presented. The study aims at demonstrating the importance of uncertainties related to wind and wave description for engineering applications and not at systematic quantification of all sources of uncertainties. The inherent variability and epistemic uncertainties associated with wind and wave data, including model tests, are discussed and their consequences on specification of design criteria are illustrated by examples. Uncertainties and limitations of the current wave database for ships are highlighted. Modelling of wind and waves often employs a mixture of mathematical, probabilistic, empirical and statistical models. Some uncertainties related to these models are presented having engineering applications in focus. Particular attention is given to stationarity or non-stationarity of sea states and wind fields, sampling variability, directionality of wind and waves and squalls. Considering waves generated in test tanks, a review of uncertainty analysis recommended in the current ITTC guidelines is given and an error analysis to be used in the model tests is suggested.