observe a remarkable improvement in agreement with measured results by the 

 calculation including the three-dimensional effect, especially at lower 

 frequencies. One of the reasons of deviation with the results by the 

 strip theory may be attributed to the logarithmic term, £nKr, in the two- 

 dimensional solution which makes the added mass infinite at zero frequency 

 limit. The three-dimensional part of the velocity potential has a term 

 which cancels the above logarithmic singularity. 



The application of the simple slender body theory, which has been 

 described in an earlier section, presents such an unrealistic result as 

 negative value of added mass and infinite increase in damping coefficient 

 at higher frequencies. Computed results for the source term a n (x) are 

 shown in Figure 8. The result by the simple slender body theory which 

 determines the near-field solution by the condition for a double body 

 shows much deviation from other theories. This fact may be the main reason 

 of the ill behavior of the slender body calculation. The fair agreement 

 between strip theory and the present calculation suggests that the source 

 term can be determined by the two-dimensional calculation without regard 

 for the three-dimensional effect, or a n (x) = V(x)A n (x). 



X 10 



_ -100 — 



-150 — 



-180 



Figure 8 - Source Distribution 



68 



