viscosity and three-dimensionality is very difficult one may split the problem 

 in a number of stages such as contact, immersion and cavity formation (i.e. 

 formation of inner free surface and spraying) and then considering each stage 

 with different assumptions. 



4) Sea loads on a vibrating ship: 



As it is known, the presently available seakeeping theories are 

 valid for rigid body motions . Therefore, as the frequency increases, the 

 wave damping vanishes and the natural frequencies obtained by using so-deter- 

 mined added masses does provide correct results, 



5) Wave forces on discontinuous structures 



In the present theories it is assumed that the change in the body 

 geometry is gradual. If, however, there are abrupt ends as in the case of 

 a barge, the flow around the ends will be different from a potential flow 

 due to vortex shedding. As a result, the forces exerted by the fluid on the 

 body may differ considerably from the results obtained from potential theory. 

 For these types of forms also the effects of viscosity should be included in 

 the calculations. 



6) Interaction problems: 



When there is more than one body and each is in close proximity to 

 the other, the flow field around each will differ from the case where the 

 other bodies are not present. Present methods of super-position of the flow 

 fields can provide reasonable approximation, provided the distance between 

 the bodies is large compared to the characteristic dimension of the largest 

 body. For configurations where the bodies are close, interaction effects 

 ought to be considered more carefully. 



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