

Figure 20. Mohr's Circle analysis, 



/XX "^ ^YY , , ^XX ^YY , „ 

 % = ^ 2 ^^ - ^ 2 ) ^°" 2a 



(21) 



^XX ^YY 



S = ( z ) sin 2a 



xy ^ 2 



(22) 



where a is the angle between the wave crest and the shoreline. S is the 

 shear stress component in the longshore direction due to the excess momentum 

 flux of oblique wave incidence. This shear stress is exerted in the + y- 

 direction on a fluid surface constant in x. The subscript nomenclature and 

 order is consistent with that normally employed for shear stresses in fluid 

 mechanics. An equal and opposite S also exists. 



For linear wave theory, the transformed components become 



S_ = E(|n - h + E(^)cos 2a 



'2 2' 

 ^2" 2' 



Syy = E(|n - ^) - E(^)cos 2a 



(23) 

 (24) 



S^, = En sina cosa 



xy 



(25) 



71 



