Application of Gaussian Wave Packets for Seakeeping Tests of Offshore Structures

Abstract

For seakeeping tests of offshore structures transient wave techniques are widely used. The method presented 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 two cases presenting a semisubmersible and a crane vessel. 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

• The wave train is well defined at any location of the tank.

• The wave elevation and spectrum can be standardized or easily adapted to any specific problem.

• The duration of the test is very short; reflections (beach) do not interfere the results. At the culmination 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 hort time.