Therefore, also 



/J ♦£«-■// KfcfflOv<.££) 



dS 



Ji (•- 



3X 8* 



The same relations hold when x is replaced by ip . Then the vertical force 



z z 



is expressed by 



w dz dn A z z ) 



+ P IT (<LlV <'''<"/. -" *.,.) - ,-;,'"" (""X..-" >U| dS (210) 



H w 3n ^^ z -- <v " 8n v-A z - r z ; 



If there is no forward speed, we have 



a 



sx W 

 1 = ' "<" I) ^w^f-^z^ri"' 



E 



This relation is called the Haskind relation. The functions X and ^ are 

 related to the solution of the radiation problem. Therefore, the above 

 relation enables the wave excitation to be evaluated without solving the 

 diffraction problem. Similar relations are obtained for pitching moment 

 too. 



76 



