Laplace domain method for computing the transient response of floating structures to irregular waves

Abstract

Traditional methods for evaluating the dynamic response of floating structures to irregular waves have been performed in either the frequency or the time domain. Whereas the computed response from the frequency-domain method is merely the steady-state response, implementing the time-domain method is usually time-consuming. In this article, an efficient pole–residue method operated in the Laplace domain to compute transient response of floating structures to irregular waves is developed, given that the frequency-domain data has been obtained from running a standard hydrodynamic package. The proposed method requires both the irregular waves and the transfer functions associated with the wave-structure system be in their pole–residue forms. From those, pole–residue form of the response can be obtained by simple pole–residue operations. Once the poles and residues of the response are known, the response time history is readily obtained. In the numerical studies, this article considers a SDOF model for the heave motion of a spar platform excited by regular and irregular waves, respectively. Numerical studies demonstrated that the proposed method is more efficient and accurate than the traditional time-domain method.