Kaplan 



naval concern, and has received increasing emphasis during the last 

 fifteen years or so by virtue of the advance of statistical methods 

 which describe the effects with greater realism than in previous 

 studies based on simplified wave representations. Major concern 

 has been devoted primarily to the problems of an advancing ship in 

 head seas, with the prime variables of concern being the heave and 

 pitch motions. Recent studies, however, have been concerned with 

 motions in oblique waves, wherein lateral motions (sway, yaw, and 

 roll) are also important, All of these studies involved large ships 

 advancing in waves, and only limited theoretical studies have been 

 developed to predict adequately the motions in all six degrees of 

 freedom under these operating conditions. A treatment of the motion 

 of a free ship with six degrees of freedom in waves is a formidable 

 problem that has not achieved a complete solution at the present 

 time, and when the influences of moorings are also included, the 

 problem is further compounded. Nevertheless, there exists a need 

 for some means of preliminary estimation of the expected motions of 

 a moored vessel, and there is sufficient hydrodynamic information 

 available to allow a study that will indicate the expected range of 

 amplitudes of motion so that the results obtained can be used as 

 guide-lines for operating personnel. 



Another related problem that is assuming more significance 

 recently is that of a moored buoy system. These smaller payloads 

 are planned for use over large ocean regions to provide a network 

 of environmental reporting stations that will yield continuous data on 

 the important properties of the ocean and atmosphere for use in 

 weather forecasting and other technologies dependent on air-ocean 

 interaction. The effective design and engineering development of 

 such systems requires an ability to predict the buoy (and hence the 

 transmitting antenna) oscillatory motions and structural acceleration 

 loadings in various seaways; the determination of the tensions along 

 the cable under various operating conditions; etc. Knowledge of such 

 results will greatly enhance the design of handling equipment for 

 both launching and retrieving of buoys at sea, and will also provide 

 basic information on system survivability under extreme environ- 

 mental conditions. 



A tool that can provide engineering estimates of such informa- 

 tion is a mathematical model that describes the essential mechanical - 

 dynamic characteristics of a moored buoy system. This mathemati- 

 cal model will be a system of equations and relationships that allows 

 the calculation of the spatial configuration, dynamic motion and 

 internal tensions of a specified moored buoy in a given excitation 

 environment. The hydrodynamic force acting on the buoy hull and 

 the forces acting on thecable system (hydrodynamic, inertial and 

 elastic) are coupled so that each affects the other, especially when 

 considering dynamic effects and rapidly varying motions. Certain 

 similarities exist between this problem and that of a moored ship, 

 together with definite differences as well. The applicability of basic 

 techniques of analysis from one problem to another provides useful 



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