ABSTRACT 



A theoretical analysis is constructed for the hydro- 

 dynamic forces acting on a system of interconnected vertical, 

 slender, axisymmetric bodies which are floating in presence 

 of incident waves. The theory is based on linearized water 

 wave potential theory and the use of slender body techniques. 

 The resulting expressions for the hydrodynannic forces are 

 used to predict the nnotions of such a system. The effects 

 of viscous damping are also estimated. 



INTRODUCTION 



A spar raft as defined here consists of several long thin bodies of 

 revolution rigidly interconnected so that they w^ill float vertically in the 

 water and support a platform or submerged ■weight. When regular waves 

 are incident on such a structure, it will generally oscillate in six degrees 

 of freedom. The purpose of this report is to provide an approximative 

 method for calculating such motions. 



The assumptions are: (1) that the spars are identical, (2) that their 

 interconnections are made in such a -way that the mass and the hydrody- 

 namic effects of the connecting members may be neglected, and (3) that 

 the individual spars are far enough apart for their hydrodynamic interac- 

 tions to be neglected. The motions of a single spar buoy have been treated 

 by Newman;^ here his method is extended to the case of N spars arranged 

 in a circle. In addition to including the hydrodynamic and inertial forces 

 on several spars, it is necessary to extend Newman's analysis to allow 

 for all six degrees of freedom. (In his problem, only three degrees of 

 freedom involved nontrivial results.) 



The basic assumptions of Newman's analysis are used here. In 

 particular, it is assumed that the virave amplitudes and body motions are 

 small enough that linearized free surface theory may be applied and that 



References are listed on page 30. 



