ABSTRACT 



Progress in developing a tool to compute large 

 amplitude ship motions is reported. In particular, a 

 method to calculate transient two-dimensional potential 

 flow about a body moving in a free surface is described. 

 The flow problem is formulated as an initial-boundary 

 value problem in which the velocity potential along the 

 free surface and the positions of the moving boundaries 

 are sought as solutions of a coupled system of 

 differential equations. An implicit finite-difference 

 method is used to advance the solution of the coupled 

 system of equations in time. The auxiliary problem of 

 computing the velocity potential inside the fluid region 

 is solved by a method which is based on boundary-fitted 

 coordinates and is directly extensible to three- 

 dimensional flows. Results from calculating the potential 

 flow about a body in forced heave motion are presented. 

 The hydrodynamic force on the body has been obtained and 

 compared with the hydrodynamic force predicted from 

 second-order perturbation theory. 



ADMINISTRATIVE INFORMATION 



This work was supported by the Numerical Ship Hydrodynamics Program at 

 the David W. Taylor Naval Ship Research and Development Center. This Program 

 is jointly sponsored by the Office of Naval Research under contract 

 N0001484AF00001, NR-334-001 , Work Unit 1542-019, and by DTNSRDC under its 

 Independent Research Program, Task Area ZR01402<U, Program Element 61152N, 

 and Work Unit 1843-045. 



INTRODUCTION 



In recent years attention of naval architects =>nd ocean engineers has 

 focused on how vessels and offshore structures react to large-amplitude ocean 

 waves. Th attention has been motivated by the capsizing of vessels in large 

 breaking saves and structural failure due to the slanming forces associated 

 with such waves. It is therefore of interest to have a method available to 

 determii • the forces on a floating body and how the body will react in these 



