A Survey of Ship Motion Stabilization 



Table 7 

 Preliminary Results of Activated Stern Fin Tests 



CONCLUSIONS AND RECOMMENDATIONS 



It should be stated that a design capability exists to produce successful in- 

 stallations of roll stabilization devices in ships. In the case of passive tanks, 

 however, much remains to be learned of the nonlinear behavior of the tank-ship 

 system. It has been indicated that many experimenters have concluded that the 

 basic lack of a physical understanding of the behavior of the tank fluid will pre- 

 vent further progress in this field. The knowledge required will probably only 

 be gained through the proper simulation of a nonlinear model. Southwest Re- 

 search will continue their efforts in this area and additional work is planned at 

 the Taylor Model Basin. 



Model and full-scale experiments will continue to be important design tools 

 in this area until more theory is understood, even though both methods also have 

 limitations. The continually changing nature of a seaway makes the collection of 

 definitive design information during full-scale sea trials an extremely difficult 

 task. While the capability for measuring sea spectra is increasing, proper ac- 

 count cannot be taken of the directional components of their effects on frequen- 

 cies of encounter. Since the roll phenomenon may be nonlinear it is additionally 

 difficult to properly normalize test data collected in this changing environment. 

 Extreme care must be exercised when design information is extracted from full 

 scale experiments. 



While the various forcing functions can be controlled to a high degree during 

 model experiments, scale effects and nonlinear ities continue to complicate this 

 approach. However, there are a large number of projects currently in progress 

 aimed at providing an understanding of these scale effects and an insight into 



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