A Study on the Numerical Prediction Method of Nonlinear Motions of a Floating Body (Part 2)

Abstract

For the people interested in the behaviors of a floating body in waves, exact nonlinear (including viscous effects) calculations of a 3-D body of arbitrary geometry in arbitrary waves must be the final goal. As a first step for this goal, we proposed in the previous paper the calculation of the motion of a 2-D floating body in a perfect fluid using MAC method. In that paper, we compared the response amplitude operator of the body in small regular waves calculated by the presented method with the experimental results and with the ones due to the linear potential theory. We also compared the calculated results on the time history of the motion of a 2-D body in transient waves with the experimental results. In both cases, the calculated results agreed well with the experimental results and with the ones due to the linear theory as well.Using MAC method, it is fairly easy to account for viscous effects in the calculation while it is quite difficult to do that in a calculation based on the potential theory. In this paper, as an extension of the previous paper, we first calculate the motion of a 2-D floating body in small regular waves in a viscous fluid and compare the response amplitude operater with experimental results and also with calculated results conducted in a perfect fluid. Next, we extend the ciculation to the motion of a 3-D floating body in a perfect fluid and compare the response amplitude operator of the body in small waves with the ones due to the linear potential theory. Finally, we calculate the hydrodynamic impact pressure on a 3-D body due to an entry into water and compare the results with existing results obtained by a perturbation theory.