CALCULATION OF DIFFRACTED WAVE HEIGHT BEHIND A 

 SEMI INFINITE JETTY 



by 



Co Garry and E° Chapus 

 La Houllle Blanche , Jan-Feb 1951 



FOREWORD 



Wave diffraction is the phenomenon in which water 

 waves are propagated into a sheltered region formed by a 

 breakwater, island „ or similar barrier which interrupts 

 a portion of an otherwise continuous wave train» The 

 ability to predict wave diffraction obviously has 

 important application in the planning and design of harbor 

 works where wave action is involved 



A theory of the diffraction of water waves passing 

 a breakwater has been adapted from theories of physical 

 optics o Putnam and Arthur investigated the theory ex- 

 perimentally for deep water waves approaching a break- 

 water with angles of incidence of 4.5°, 90°, and 135° ■> 

 measured at distances varying from 3°38 to 17o85 wave 

 lengths from the breakwater and compared results both 

 with the somewhat complicated rigorous theory and a 

 simplified solution employing approximations (Trans- 

 actions;, American Geophysical Union, Vol., 29, No A 9 

 August 194.8)o The application of diffraction theory 

 to water waves passing through a breakwater gap, for 

 both deep and shallow water waves in uniform depth, has 

 been investigated experimentally by Blue and Johnson» 

 (Transactions, American Geophysical Union, Volo 30, 

 NOo 5j> October 194-9 )<> Experiments reported in the follow- 

 ing translation supplement the -work of Putnam and Arthur, 

 covering diffracted shallow water wave heights along the 

 breakwater itself in the sheltered region, for angles of 

 incidence corresponding to those tested by Putnam and 

 Arthur 



This article has a double objectives first, to translate Into 

 curves or asymptotic formulaevl) results derived by the method 

 developed by Messrs c Putnam and Arthur for the calculation of the 

 diffracted wave height behind a semi-infinite jetty 5 second, to 

 report certain experiments which had as their objective the 

 verification of this theory 



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