A New Appraisal of Strip Theory 



2.0 



3.0 



4.0 



5.0 



B ui\ 



2g 



Fig. 69 - k^ versus S 



c. His program can handle any arbitrary ship section which can be defined 

 by either (1) an arbitrary number of parameters or, even better (2) a set of off- 

 sets for the section [45]. 



d. Extension to the problem of horizontal oscillation can also be made for 

 lateral ship motions. 



It follows from c. that Porter's program will discriminate between the 

 added mass and damping of two sections of identical section coefficients and 

 beam- draft ratio but differing in detailed section shape. Thus it should prove 

 more flexible than programs tied to particular section families such as the 

 Lewis or Landweber sections. 



CALCULATION OF EXCITATION FORCE AND MOMENT 



The second main category of the loads imposed on the ship hull are those 

 due to wave action. As a result of the linearization of the problem, these forces 

 and moments can be assumed to act independently on the ship which is moving 

 at constant speed but is otherwise restrained from any translatory or ai^ular 

 displacements. 



Since there is no distinction, as far as hydrodynamic forces and moments 

 are concerned, between a restrained ship in a vertically oscillating fluid and an 



339 



