be faced for effective laboratory investigation of these processes and 

 suggested means for overcoming the difficulties. 



Several significant discoveries about wind-wave generation and wind 

 stress on water have been made in laboratory studies, sometimes with very 

 small wind-wave facilities. There is no doubt about the value of labora- 

 tory wind-wave research facilities by well-qualified investigators for 

 basic research dealing with the interaction of air and sea. 



This study was undertaken to determine design parameters which should 

 be recommended for a wind-wave channel to be used in coastal engineering 

 studies in much the same way that tanks with mechanical wave generators 

 are used. During the study it was foimd that the process of transferring 

 mechanical energy from the airstream to the water is infinitely more com- 

 plex than the process of transferring mechanical energy from one location 

 to another by means of gravity waves. Further, it was found that a satis- 

 factory technique for modeling wave generation and wind stress on water in 

 a laboratory facility does not yet exist. There are excellent reasons for 

 doiibting that a technology satisfactory for all purposes can be developed. 



Thus, while the study had been expected to culminate in the recommen- 

 dation of design parameters, it does not. Rather, it concludes that 

 although a combination wind tunnel-wave channel could be a great aid to 

 fundamental research in air-sea interaction processes, the state-of-the- 

 art of modeling air-water interaction processes in the laboratory has not 

 advanced to a level which provides any assurance that the validity of 

 laboratory studies of wave effects on beaches or manmade structures is 

 improved for engineering application by using wind to generate or modify 

 laboratory waves. 



Since these conclusions were unexpected at the initiation of the study, 

 it seems worthwhile to note that several other investigators with con- 

 siderable experience in the laboratory study of momentum exchange between 

 air and water independently arrived at substantially this opinion. A few 

 of the published quotations are given below. 



"...waves in laboratory tanks seem to grow differently from waves in 

 the ocean..." (Wu, 1972, p. 163). 



Miles (1967, p. 166), in discussing the generation of gravity waves in 

 the laboratory by processes believed to be important in nature, stated: 

 "The laboratory generation of the later waves at an^jlitudes that are 

 adequate for quantitative measurement appears to require a mechanical wave 

 maker. Moreover, it appears difficult to obtain accurate measurements of 

 wind- induced growth rates for such waves over attainable fetches..." 



Hidy and Plate (1965) presented a plot of normalized spectra which 

 showed that the width of the spectrum peak for wind-generated waves tends 

 to be much broader in the field than in the laboratory. 



