Preface to Chapter 1 



It has been the author's experience that tlie sokition 

 of any practical problem connected with wave motion is 

 often accompanied by a lai'ge amount of fumbling. 

 The reason for this is that information on waves is widely 

 scattered in various textliooks, written by mathematical 

 physicists, and is often presented in a form which makes 

 direct application to engineering problems difficult. 

 Furthermore, the author's early reading in oceanography 

 has shown him that some of the basic concepts of hy- 

 drodynamics have often Ijeen disregarded, possibly be- 

 cause of want of easy reference. Apijendix A was pre- 

 pared, therefore, as a ready reference to give a concise 

 summary of the theory of wave motion on the basis of 

 classical hydrodynamics. 



Rapid progress in the de\'clo|)meul of the theory of 

 ship motions in a complex seaway has taken place follow- 

 ing the appearance of the paper by St. Denis and Pier- 

 son (Transactions SN^Aj\IE, 1953). This activity has 

 been based on the description of an irregular sea surface 

 by an energy spectrum. In this connection the term 

 "Neumann's spectrum" has so often been used that the 

 basis of its development appears to be forgotten. An 

 effort has been made, therefore, to exjjound Neumann's 

 work rather completely in Appendix B, while in the 

 text only a relati\-el.v brief summary appears. 



The author has found that at present oceanographic 

 knowledge is rather disorganized in so far as the tran.s- 

 mission of energy from wind to water, the growth of 

 waves under the action of wind, and the wave size indi- 

 cated by the spectrum of a complex seaway are con- 

 cerned. Very few experts appear to agree on solutions 

 to these problems. Yet it is futile to expect a satis- 



factory quantitative description of ship molions or ship 

 stresses at sea without a good knowledge of tlie com- 

 plex seaway which causes them. As a result of this 

 state of affairs, Chapter 1 has become more detailed 

 and voluminous than was originally intended. 



During the preparation of this monograph, two ex- 

 tensive summaries of the existing knowledge on ocean 

 waves appeared in the press, the first by l'\ Ursell (Ref- 

 erence M), and the second by H. U. Roll (Reference L). 



The general plan of exposition in these two summaries 

 is similar to the one ])resented here by the author. None 

 of these three summaries eliminates the need for the 

 others, since each author has emphasized different as- 

 pects of this vast and complex subject. Tiie present 

 exposition, intended es])eciallv for stimulation of re- 

 search, is much more critical than the others and stresses 

 shortcomings no less than achie\'ements. 



The cxpftsition of sea-wave properties given in this 

 monograph is oriented to its ultimate use in naval archi- 

 tecture and in ship navigation. It is, therefore, incom- 

 plete in regard to many other fields of endeavor. The 

 ultimate development which is the interest of the present 

 monograph would con.sist of a specific formulation of a 

 directional wave spectrum as a function of meteorological 

 conditions. Merely empirical attempts to secure such 

 knowledge of the complex sea ha\'e not yielded a satis- 

 factory solution. It is tlie author's opinion that a 

 general theoretical development is also needed for achiev- 

 ing this ol)jective. A comprehensive review of the 

 theoretical work and of the laboratory and open-air 

 observations connected with it was therefore included 

 in the monograph. 



New York, N.Y. 

 Januarv, 19(50 



B. V. KORVIN — Kroukovsky 



