A Time-Domain Method for Hydroelastic Analysis of A Moored Oil Storage Vessel in Wind, Irregular Waves and Currents

The hydroelastic behavior of a moored oil storage vessel subjected to arbitrary time-dependent external loads, which include wind, waves, and currents with different incident directions, is investigated with the time-domain modal expansion method. First, the water boundary integral equations on the body surface of a quarter model, which can be obtained via the free-surface Green's function method, are established. Then, the time-dependent elastic deflection of the moored oil storage vessel is expressed by a superposition of modal functions and corresponding modal amplitudes, and a Galerkin scheme is applied to derive the linear system of equations for the modal amplitudes. The second-order linear differential equations for modal amplitudes are solved via the fourth-order Runge-Kutta method. The present model is validated against existing frequency domain results for a truncated cylinder and a VLFS. Numerical calculations for the moored oil storage vessel are then conducted to obtain the time series of various modal amplitudes and elastic displacements of the measurement points and the corresponding spectra with different incident directions.