Wave Excitationless Ships Forms 



The approximate values of the heaving force is obtained by Eq. (4) as shown 

 in Fig. 3. 



At relatively low frequency range, the buoyancy is greater than the inertia 

 force (or under cancel), and the heaving force will be inphase with the wave ele- 

 vation. At oJq given by Eq. (5), heaving force is zero, and at higher frequency 

 than ojp, the inertia force exceeds (over cancels) the buoyancy, i.e., the heaving 

 force at this frequency range will be 180 degrees out-of-phase with the wave 

 elevation. 



It is also shown in Fig. 3 that 

 breadth of the strut decreases. 



shifts toward lower frequency when the 



0.5 1.0 1.5 2.0 2.5 f-7 



Fig. 3 - Calculated heaving force of circular cylinder type models 



2) To check the above described results, experiments were conducted on a 

 model of the following size: 



Diameter - 2a = 20 cm 



Breadth of the strut - B = 15 cm (1.5a), 10 cm (a), and 5 cm (0.5a) 



Length = 50 cm (with end plates). 



To prevent the sway and pitch of the model a guide is attached to the model 

 as shown in Fig. 4. The heaving force was measured by a rigid spring attached 

 by a linear transformer as a pick-up. 



387 



