Hydrodynamic interaction effects between VLFS and submerged plate are presented in this paper. A composite grid method has been employed to compute the interaction effects of hydrodynamic forces on VLFS with or without submerged plate.The fully nonlinear free surface flow problem, which involves the overturning and breaking waves, is solved using the finite difference method. In order to investigate the interaction effect, the fore part of VLFS has forced to heave sinusoidally with the submerged plate or not. Furthermore, the reflective wave by VLFS, which acts on the submerged plate heaving near a free surface, is considered to estimate the hydrodynamic forces. The added mass and damping forces are shown to be influenced strongly by the interation effects and are presented as a function of oscillation periods. Namely, the added mass on the whole are increased due to the interference effects between VLFS and submerged plate regardless of oscillation periods. On the other hand, the damping forces become larger at short oscillation periods because of impinging wave which came from the reflection by the other structure. The influence of added mass and damping forces means that the response amplitude of VLFS is decreasing. These results reaffirm that the effect of submerged plate on hydroelastic deflection is significant at short oscillation periods. The results obtained by the present numerical simulation are compared with those obtained by the experiments, and it shows a good agrrement.
