FOREWORD 



It has been a great honor to deliver the fourth in this series of 

 lectures because of the prestige of this laboratory and the distinguished 

 lecturers before me. The previous lectures have all been of a rather 

 theoretical nature; I have been asked instead to emphasize problems from a 

 more applied point of view. On the one hand, this appears to be an easy 

 course to follow, since many important areas of naval hydrodynamics lack 

 the precise physical description required for detailed mathematical 

 analysis. On the other hand, there is a real problem of selection, since 

 so much of the present work in hydrodynamics has originated here at the 

 Naval Ship Research and Development Center (NSRDC) . With this caveat then, 

 it will be understandable that I have chosen for discussion a subject of 

 long standing interest in naval hydrodynamics, generally, and one of partic- 

 ular interest to this laboratory, namely, cavitation. Even this is too 

 broad a topic for only a few lectures and I have restricted myself to two 

 topics; these are, cavitation inception on smooth bodies and some effects 

 of developed cavitation in internal flows. There are many instances of 

 cavitation in internal flows. The testing of cavitating bodies in water 

 tunnels is one, and that of cavitation in a ducted propulsion system is 

 another. In both situations the flow is internally confined and is, there- 

 fore, geometrically complex. System interactions can then occur which, 

 particularly for unsteady flows, leads to great difficulties of experi- 

 mentation and interpretation. 



I would like to acknowledge the help and stimulating discussions with 

 many of the laboratory staff. These are too many to mention here, but I 

 would like to reserve special thanks to Justin McCarthy, William Morgan, 

 and Mrs. Shirley Childers for making my lectureship a memorable occasion. 

 Finally, I would like to express my gratitude to my friend and former 

 teacher, Milton Plesset, for his witty and insightful counsel. 



