ANALYSES OF HINGED WAVEMAKERS FOR RANDOM WAVES

Abstract

The theoretical dimensionless frequency response functions for the wavemaker stroke spectrum, Qs(iu), and for the wavemaker dynamic pressure moment spectrum, Q^{m), were verified experimentally in the Oregon State University-Wave Research Facility (OSU-WRF) from random waves which were simulated from two types of two-parameter theoretical design wave spectra. The random motions of the wavemaker were first digitally simulated by a unique inverse stacked FFT algorithm which were then used to drive the wavemaker through digital-to-analog converters (DAC). The dimensionless frequency response function for the hydrodynamic pressure moment spectrum was not measured directly but was computed from the dynamic covariance equations for a hinged wavemaker of variable-draft by linear combinations of related dimensionless frequency response functions and cross-spectral estimates. The measured estimates were found to agree reasonably well with the analytical approximations, and these measured stochastic hydrodynamic pressure moment estimates on a hinged wavemaker of variable draft are believed to be unique.