Gaussian wave packets — a new approach to seakeeping testsof ocean structures

Abstract

The transient wave train techniques has been widely used in testing ocean structures. The methodpresented here is based on a special Gauss-modulated amplitude spectrum. These wave groups of limited length can be superimposed, the actual surface elevation being a function of packet characteristics and initial time lag. The application of this technique is demonstrated in three cases presenting a semisubmersible,an articulated tower and a floating oil skimmer. It is shown, that a particular problem needs a tailored wave packet containing sufficient energy all over the relevant frequency range. These packets are designed by superimposing individual Gaussian wave groups. The new seakeeping test techniques has the following advantages u - The wave train is well defined at any location of the tank. - The wave elevation and spectrum can be standardised or easily adapted to any specific problem. - The duration of the test is very short; reflections (beach) do not interfere the results. At theculmination point the length of the wave train is small. This facilitates short duration seakeeping and manoeuvring tests. - The results show high resolution and are in good agreement with regular wave test data. Summarising, the Gaussian wave packet method is a versatile technique yielding precise and highly resoluted results in a short time.