Distribution of Hydrodynamic Forces on a Shipnnodel 



Comparison of Theory and Experiment 



For a number of cases the experimental results are compared with theory. 

 First of all the damping cross-coupling coefficients are considered. From Eqs. 

 (13) it follows that: 



= I N'xdx 



+ Vm 



(16) 



dx - Vm 



The first term in both expressions is the cross- coupling coefficient for zero 

 forward speed. For a fore and aft symmetrical ship this term is equal to zero. 

 For such a ship the resulting expressions are equal in magnitude but have oppo- 

 site sign, which is in agreement with the result found by Timman and Newman 

 [7]. The experiments confirm this fact as shown in Fig. 13 where e and E are 

 plotted on a base of forward speed as a function of the frequency of oscillation. 

 The magnitude of the speed dependent parts of the coefficients is equal within 

 very close limits. Extrapolation to zero speed shows that the e and E lines in- 

 tersect in one point which should represent the zero speed cross- coupling co- 

 efficient. 



Using Grim's two-dimensional solution for damping and added mass at zero 

 speed [9] the coefficients e and E were also calculated according to the Eqs. 

 (16). The distribution of added mass and damping coefficient for zero speed is 

 given in Fig. 12 and the calculated damping cross- coupling coefficients are 

 shown in Fig. 13. 



^ 



^ 



^S 



Fn = 



Fn = 



Fig. 12 - Calculated distribution of a and b for zero speed 



221-249 O - 66 - 17 



241 



