Giddings and Wermter 



_i 4 — 



3 — 



ROLL RESPONSE 

 BOW SEAS (135°) 

 FROUDE NO. = 0.08 

 WITH OUT BILGE KEELS 



I 2 3 4 5 6 

 MODEL FREQ OF ENCOUNTER RAD/SEC 

 J I I I I \ I I I 



J L 



0.2 0.4 0.6 0.8 1.0 

 SHIP FREQ OF ENCOUNTER, Wg , RAD /SEC 



0.5 



1.0 

 TUNING FACTOR, A,^ 



Fig. 11 - Effectiveness of 

 passive anti- rolling tanks 



In continuing the model study on the AGOR class of ship, the Davidson Lab- 

 oratory conducted experiments in regular waves to determine speed and wave 

 height effects [42]. This study concluded that an increase in the height of regu- 

 lar beam waves decreases the effectiveness of the tank system and the peak of 

 the unstabilized roll response moves to a slightly lower frequency. Figure 12 

 shows a comparison of the various roll responses derived from experiments 

 conducted by Refs. 41 and 42. 



The speed study indicated the obvious result of an increase in roll damping 

 with increased speed for the unstabilized ship condition and an increase in the 

 stabilized roll amplitudes (decreasing tank effectiveness with increased speed). 



ARIS-3 Passive Tanks. The ARIS-3 is a design for a 496-foot Advanced 

 Range Instrumentation Ship of 13,600 tons displacement. Bench tests were con- 

 ducted at the David Taylor Model Basin on a 1/20- scale model passive tank. In 

 addition to determining the depth of water required for properly tuned operation. 



764 



