Kim and Mercier 



DISCUSSION 



The chief findings of these investigations may be given as : 



1. The vertical wave-induced forces on relatively slender, ver- 

 tically-oriented, isolated floats can be evaluated with adequate ac- 

 curacy according to available analytical procedures (Eq.34). 



2. The introduction of a hinge to permit lateral pendulum-like 

 motions of the lower (attenuator) portion of the float produces a large 

 reduction of the lateral wave -induced load. 



3. This hinge does not have an appreciable effect on the vertical 

 wave-induced forces. 



4. Articulated Model Island tests indicate that an important inter- 

 action effect on heave motion occurs. This may be due to hydrodyna- 

 mic effects, or to some kind of elastic or connecting mechanism ef- 

 fects. A simplified elastic normal mode analysis does not appear to 

 indicate "classical" linear elastic effects leading to the interesting 

 "tail wagging" phenomena found in the tests. 



5. The vertical wave -induced forces acting on rigidly-fixed floats 

 in an array like that of the articulated model island show an appreci- 

 able effect of interaction, principally on floats in the interior of the 

 array. There is, however, a small fore-and-aft asymmetry of this 

 heave producing force, with the stern row of floats experiencing slight- 

 ly higher forces than the bow but still less than the middle floats. It is 

 felt that this asymmetry of the exciting force is not sufficient to pro- 

 duce the substantial "tail wagging" of the motions tests. 



6. The longitudinal wave -induced forces acting on the rigidly-fixed 

 array of floats show only a modest effect of interaction, which is 

 greater for high frequencies than for low. 



7. Scale effects on wave -induced forces acting on a large rigidly- 

 fixed array of floats were investigated by testing a model whose size 

 is much smaller than would ordinarily be selected for hydrodynamic 

 testing. The forces measured on the small models were somewhat 

 lower than those obtained with the larger model. The trends of va- 

 riations of forces with frequency are the same for both sizes of models. 

 It is considered that models sizes ordinarily selected for platform 

 motions tests are generally satisfactory and free of important scale 

 effects except possibly for some viscous effect on damping forces for 



848 



