Hydrodynamic interactions between waves and cylinder arrays of relative motions composed of truncated floating cylinders with five degrees of freedom

Abstract

The hydrodynamic interactions between waves and a truncated floating circular cylinder array were examined in this work. Each cylinder of the array is allowed to oscillate with five degrees of freedom (DOFs), and there can be relative motions among different cylinders. The hydrodynamic responses of such arrays in the presence of ambient incident waves were studied using a semi-analytical technique, in which, the unknown coefficients of radiation–diffraction velocity potentials caused by array motions were expressed by the linear combination of each cylinder’s to-be-calculated oscillation amplitudes in each direction. Then, for each cylinder in the array, the amplitude of each degree of freedom was computed. Variations in the oscillation amplitudes of the cylinders in the array with wavenumbers for various incidence angles and column spacing, and amplitude distributions of free surface elevation for various wavenumbers were given. Additionally, extensions to the situation of multidirectional irregular waves were presented. Last but not least, we examined the effects of other DOFs (nonheave) on hydrodynamic responses and wave energy extraction performances (capture width w and interaction factor q) by comparing the results obtained by the 5-DOF and the 1-DOF (heave) models. In terms of response amplitude and wave energy extraction performance, the 5-DOF model’s results were significantly different from those of the 1-DOF model. Therefore, it is suggested to use the 5-DOF model to analyze such cylindrical arrays.