2. A computer program which permits the rapid computation of the exciting forces; 



3. A better understanding of damping mechanisms; 



4. Improved knowledge of virtual mass; 



5. Suitable vibration specifications or limits of acceptability for vibration of the system 

 under study; and 



6. Full-scale program of applicability studies. 



At this time a Basic Computer Program exists at the Model Basin and is applicable to 

 any mechanical system, such as a ship hull or main propulsion plant. The response of a ship 

 to simple harmonic driving forces is a function already available in the Basic Computer Pro- 

 gram. Studies of hull mobility, when driven by a unit exciting force, is frequently carried out. 

 Vertical bending modes, as well as other modes, are also computed regularly. The response 

 of shafting systems, is also regularly computed. It is fair to say that a "Basic Computer Pro- 

 gram" which permits the study of the response of a given mechanical system presently ex- 

 ists. A handbook on "Coded Vibration Problems" which describes the individual problems, 

 is being prepared. Another project, "Mechanized Calculation of Ship Parameters," is essen- 

 tially complete. This project is intended to simplify the determination of computer inputs 

 for studies of hull response. 



The analysis of wake patterns, necessary to the development of exciting forces, al- 

 ready exists. A computer program, which permits the development of wake harmonics from 

 wake patterns, also exists. The calculation of propeller-exciting forces in various wake 

 distributions has been developed by Pien. What remains to be done in this area, however, 

 is the development of the process to that state of perfection which would permit the rapid 

 determination of propeller forces in a routine manner. For example, the operation of any 

 given propeller in a given wake pattern requires considerable detailed effort in working from 

 the propeller drawings. Presumably, this process can be mechanized. 



Further R&D effort is required. Although the factors of damping and virtual mass can 

 be handled at the present time in the existing basic program, the constants used, particularly 

 that of damping, are considered inadequate. A project has been initiated during the current 

 year to develop a program on Hull Damping. 



Vibration specifications, or criteria, is considered a long-range or "live" project. 

 Our project on "Vibration Norms" is intended to serve this purpose but, even when completed, 

 must be continually updated. In this regard, criteria or specifications for machinery vibration 

 is much further advanced. 



The full-scale program of applicability studies is also an active or "live" program. 

 Whenever possible, full-scale studies (such as the NS SAVANNAH studies) are carried out 

 to assist in developing our prediction techniques. 



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