The development of a programmable wave generator for the simulation of sea state

Christian, Colin Douglas (1973) The development of a programmable wave generator for the simulation of sea state. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

A programmable wave generator suitable for the modelling of a variety of sea states was developed and used to simulate prototype and theoretical wave spectra. Prototype wave records from different locations were analysed in order to determine the spectral form for typical coastal conditions. Different methods were used in certain cases to show how the spectral shape varied with changes in the computation process. The wave generator, which was developed, consisted of a piston type paddle suspended from a carriage running on linear bearings. Motivation was provided by a double-acting hydraulic ram. A closed loop control circuit was employed to control the motion of the p d d l e. A purpose-built punched tape interface, incorporating sequencing logic and digital-to-analogue conversion, provided the command signal for the programmed waves. The command tapes were generated on a digital computer by filtering random numbers using a fast Fourier transform method. The filter shape was determined by considering the desired spectral shape and the paddle amplitude to wave amplitude relationship predicted by small amplitude theory. The overall performance of the system was assessed by simulating the spectra derived from the prototype records and Moskowitz spectrum.

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