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Publicações
Guedes Soares, C. e Veltcheva, A. (2004), “Wave Data Analysis by Hilbert Huang Transform and Conventional Discretization Methods”, Proceedings of the 29th International Conference on Coastal Engineering (ICCE´04), 19-24 September, Lisbon, Portugal, Paper nº 331
The proper choice of analyzing technique is very important for correct understanding of the examined phenomenon. Two different methods for data analysis conventional wave discretization methods and Hilbert Huang Transform (HHT) method are utilized for the investigation of real sea waves in this work. The field data were collected at Portuguese coast, as sea surface elevation records are 20 min long at sampling data rate of 0.78 sec. First the conventional wave data analysis methods are discussed in details. These methods are burden with traditional concept of sea waves, as a sine wave, while the real sea waves are nonlinear and non-stationary and their profile is asymmetrical with respect to the zero level, with sharp crests and flat troughs. Existence of small ripples, riding longer waves, as well as appearance of a lot of small waves due to wave breaking, complicates considerably the sea surface profile. Application of conventional methods for determination of individual waves, like zero-crossing (ZC) method, often faces with difficulties how to treat these small amplitude waves. In some works they are considered as noise and are removed from the data. The ignorance of these really existent futures of sea waves leads to incompleteness and often to misinterpretation of the recorded sea state and in this way the analyzing method can distort the investigated phenomenon.
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