Compendium of Ship Motion Calculations Using Linear Time-Domain Analysis

Abstract

Over the past four years a three-dimensional time-domain seakeeping computer code has been developed at The University of Michigan. The code uses linear system theory to determine the hydrodynamic forces acting on a vessel due to forced oscillations (radiation forces) or due to incident waves (exciting forces). It is based on the Neumann_Kelvin potential flow model and solves the problem directly in the time domain rather than the traditional frequency domain. In the Neumann_Kelvin approach the body boundary condition is satisfied on the exact body surface and the linearized free surface condition is used. This approach brings in the three-dimensionality of the body surface and some of the forward speed effects. It does not account for the nonlinearities of the free surface and neglects certain other forward speed effects. This report is a complete summary of the computations made using the time-domain program.