A Vortex Theory for the Maneuvering Ship 



22.7. Now we come back to the mathematical model which has been the 

 starting point of the present paper. Obviously such a model could give too 

 many remarks and criticisms. For instance, we consider as a fact that a wake 

 exists, but the real structure of the wake is in connection with the mechanism of 

 the transport into this wake of the vorticity which originates in the boundary 

 layer. Certainly the approximation of the quasi-perfect fluid is not a refined 

 one. The present theory does not stand on the same refined level as the theory 

 of the wings of finite span. Many improvements would be desirable from a sci- 

 entific point of view. But, for practical purposes, we have for the time being to 

 admit semi -empirical theories. The quasi- steady motion theory which until now 

 has been the only one practically used, is also a semi-empirical theory. The 

 most important point in this paper is the following: In practice, have we or have 

 we not to take into consideration the facts disclosed by harmonic forced motions 

 tests? 



We don't answer this question. But we sincerely hope that it is worth 

 putting. 



REFERENCES 



1. W. E. Cummins, "The Impulse Response Function and Ship Motions, 

 D.T.M.B. Report 1661, Oct. 1962. 



2. Th. von Karman and W. R. Sears, "Airfoil Theory for Non-Uniform Mo- 

 tions," Journal of the Aeronautical Sciences, Vol. 5, No. 10, Aug. 1938. 



3. P. Casal, "Sur les Qualites Evolutives des Navires" (Thesis, 1950). 



4. R. Brard, "Maneuvering of Ships in Deep Water in Shallow Water and in 

 Canals," SNAME, Vol. 59, pp. 229-257, 1951. 



5. S. B. Spangler, A. H. Sacks, J. N. Nielsen, "The Effect of Flow Separation 

 from the Hull on the Stability of a High-Speed Submarine," Vidya Report 

 No. 107, Aug. 1963, for O.N.R. and D.T.M.B. 



6. E. J. Rodgers, "Vorticity Generation of a Body of Revolution at an Angle of 

 Attack," Paper No. 64-FE.S (read before the American Society of Mechani- 

 cal Engineers), Philadelphia, May 1964. 



7. M. Sevik, "Lift on an Oscillating Body of Revolution," Am. Inst, of Aeron. 

 and Astronautics Journal, pp. 302-306, Feb. 1964. 



8. R. Brard, "Mouvements Plans Non Permanents d'un Profil Deformable," 

 Bulletin de I'Association Technique Maritime et Aeronautique, Paris, 1963. 



907 



