A pole–residue method for computing the transient hydroelastic responses of VLFSs

Abstract

Conventional methods for computing hydroelastic responses in very large floating structures (VLFSs) typically involve either frequency domain or time domain approaches. While frequency domain methods are constrained to steady-state responses, time domain methods are generally less efficient. This paper introduces an innovative Laplace domain pole–residue approach to calculate the hydroelastic transient response of a VLFS, incorporating hydroelasticity through a discrete-module-beam-bending model. To implement the proposed method, frequency domain data must first be obtained using a standard hydrodynamic package. Additionally, the method requires expressing both external loadings and system transfer functions in a pole–residue form. Subsequently, the pole–residue form of the response is derived through straightforward pole–residue operations. Once the poles and residues of the response are identified, the response time history can be readily determined. This study specifically concentrates on computing the transient hydroelastic response of a VLFS in calm water conditions subjected to highly irregular loading. In the numerical study, the VLFS is modeled as a continuous shallow-draft flexible box, divided into 8 submodules connected by 7 beams. Frequency-dependent hydrodynamic parameters are calculated by the commercial software SESAM. The heave responses of the first and second submodules under an impact loading are investigated and compared with those obtained by a time-domain method. Numerical studies demonstrate that the proposed pole–residue method surpasses traditional time-domain methods in terms of both efficiency and accuracy.