Real Sea Waves Research Articles

Identification of the components of wave spectra by the Hilbert Huang transform method

The Hilbert Huang Transform method is applied to identify different components of the spectra of real sea waves. Field data collected at the Portuguese coast are used in this study. The ability of Empirical Mode Decomposition to extract the different oscillation modes, embedded in the sea surface elevation records, is demonstrated. The contribution of different Intrinsic Mode Functions to the wave data is examined.

An evaluation of directional analysis techniques for multidirectional, partially reflected waves Part 2: application to field data

Based on the findings of a numerical investigation, presented in the Part 1 companion paper, two methods of directional analysis, the maximum likelihood method (MLM) and the Bayesian directional method (BDM) are applied to over 80 field data sets. These cover a wide range of environmental conditions, for which multidirectional, partially reflective sea states exist. The results show that trends similar to those found using the numerical simulations are observed in the field estimates of relative predictions of incident significant wave height, average reflection coefficients, main directions and directional spreading. It is concluded that overall the BDM produces the more accurate results when applied to real sea waves.

Experimental Study for Directional Wave Force on a Column

Real sea wave is quite random in amplitndes, periods and propagating directions. Offshore sea waves, therefore, have characteristics of “directional randomness”. Directional random waves in the offshore consist of the component waves each propagating in different directions in shallow area. Some coastal structures constructed in deep water area should be designed for directional random waves. The experiment for the directional wave force are done. The target structure is a column, which is the simplest component in coastal structures. The wave force on a column in directional seas is compared with that in uni-directional waves.

LOAD ANALYSIS FROM WAVE GROUPS

At the present time sea wave is described by means of two theoretical models, the first is based on regular waves, components of which do not change in time and space, and the second model is based on irregular waves, components of which are randomly changed. The latter coincides to the greater extent with the rolling sea, but even this model does not characterize it to the full» Taking sea wave for a random process, the model of irregular waves does not take into account the sequence of their alternation. Prom the point of view of probability, on which the model of irregular waves is based, the maximum wave may be followed by the minimum wave, and the greater period may be followed by the smallest one. The real sea wave, especially in shore zone, where the main engineering constructions are placed, is characterized by clearly expressed group structure, which includes alternation of a number of great and small waves and the maximum wave is always followed by the wave having almost the same parameters.

Wind Waves at Sea, Breakers and Surf

SEA WAVES are as unruly as ever ; but their characteristics are becoming more predictable as knowledge accumulates. The pioneer work of Arago and Stevenson Was energetically extended by the American army engineer Gaillard, whose book on "Wave Action" published in 1904 has recently been reprinted. The aim of theory has always been to extract from the reality simpler ideas that are comprehensible ; that real sea waves are complicated is sufficiently evident from the stereophotographs and contour diagrams prepared in 1939 by Schumacher. The first mathematical guess at the nature of a sea wave was made by Gerstner in 1802, and the later theories, most notably those of Stokes and Rayleigh, have provided a sound basis for the Work of the physicist and engineer. Wind Waves at Sea, Breakers and Surf By Henry B. Bigelow W. T. Edmondson. (United States Navy Department: Hydrographic Office: H.O. Pub. No. 602.) Pp. xii + 177 + 24 plates. (Washington, D.C.: Hydrographic Office and Government Printing Office, 1947.) 2.80 dollars.