Gerritsma and Beukelman 



are neglected in a calculation of the heaving and pitching motions. In this calcu- 

 lation we used coefficients of the motion equations, which were determined by 

 forced oscillation tests. In comparison with the calculation where the cross- 

 coupling terms are included and also in comparison with the measured motions, 

 an important influence is observed, as shown in Fig. 1, which is taken from 

 Ref. [5]. Further analysis showed that the discrepancies between the coupled 

 and uncoupled motions were mainly due to the damping cross- coupling terms. 



The influence of forward speed has been discussed to some extent in Voss- 

 ers' thesis [6]. From a first order slender body theory it was found that the 

 distribution of the hydrodynamic forces along an oscillating slender body is not 

 influenced by forward speed. Vossers concluded that the inclusion of speed 

 dependent damping cross-coupling terms is not in agreement with the use of a 



UJ UJ 



0.75 1.00 1.25 1.50 1.75 



Yl ^WAVE LENGTH RATIO 



Fig. 1 - Influence of cross-coupling 

 220 



