HAMS: A Frequency-Domain Preprocessor for Wave-Structure Interactions—Theory, Development, and Application

Abstract

This paper presents the theoretical background, the numerical implementation, and the applications of a new software that has been developed in recent years for the analysis of wave-structure interactions. The software is developed in the frequency domain, as a preprocessor of computing the wave excitation force, the added mass, and the wave radiation damping, for input to a time-domain solver via the Fourier cosine and sine transforms. In addition, it can also predict the motion responses of a marine structure with sufficient accuracy, with or without the presence of the mooring system. Unlike other frequency-domain software, such as WAMIT® and Hydrostar®, the present software currently employs the least squares method in association with a partially extended boundary integral equation method to remove the so-called “irregular frequencies”. Calculation of the free-surface Green’s function employs a combination of fast-convergent series expansions in different parametric sub-regions. The solution of the resultant linear algebraic system employs the lower-upper (LU) decomposition method. Symmetry properties can be exploited, and the open multi-processing (OpenMP) parallelization technique can be applied to reduce the computation burden. The accuracy and the efficiency of the developed software are finally confirmed by numerical validations on a floating ellipsoid benchmark case and the OC4 DeepCwind semisubmersible floating wind turbine in practice. A free executable version of the software is available to the research communities with the hope of facilitating advancements in the researches that are relevant to ocean engineering and marine renewable energies.