WAVE DIFFRACTION FOR OBLIQUE INCIDENCE 



by 

 Henri La combe 

 Principal Hydrographies Engineer 

 Coraite Central D'Oceanographie et D' Etude Das Cotes 



FOREWORD 



The following article was translated from 

 the December 1950 Information Bulletin, Coalite 

 Central d'Oceanographie et d'Etudes des Cotes 

 It is published here as a means of informing 

 interested readers of the interest in and pro- 

 gress being made in foreign countries on ocean 

 wave problemSo Numbers in parentheses refer to 

 the bibliography following the article „ 



Status of the Question in June 1950 



In the Information Bulletin of Comite Central d'Oceanographie 

 et d'Etudes des Cotes for June 1949 s we discussed the general features 

 of a study on wave diffraction which had been published in consider- 

 able detail in the Annales Hydro graphique of 194-9 (1). We pro- 

 posed in that article that diffraction for normal incidence could 

 be studied by an almost exclusively graphic method which would not 

 differ greatly from the rigorous solution in the case of semi- 

 infinite breakwaters*- „ The method was equally applicable to the 

 diffraction caused by vertical obstacles , with the condition that 

 the waves approach the obstacles normally,, 



An American study by Blue and Johnson (5) discussed the the- 

 oretical solution, which was already known,, and extended it by 

 means of a certain approximation to the case of openings, but sole- 

 ly for the situation where the waves approached normal to the open- 

 ing,, Photographs obtained in the course of the study on "the model 

 show the existence of areas of agitation analogous to those that 

 we had noted, and which are encountered also in the emission pattern 

 of certain submarine acoustic apparatus and radio antenna systems „ 

 This study further had the advantage of showing clearly the effect 

 of what one may call wave guides, defining the opening and which 

 are constituted by vertical walls connected to the breakwater and 

 directed toward the exterior of the port in a direction opposite 

 to that of propagation,, These guides had the effect of making a 

 little more rigorous the simplified solution of Putnam and Arthur (4) 



* Lamb (2) pp. 538-540 5 Bateman (3) pp» 476-490$ Putnam and Arthur (4) 



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