E = E + 

 k 



E = 

 P 



16 



16 



PgH^L 



(2-38) 



Subscripts k and p refer to kinetic and potential energies. Total average 

 wave energy per unit surface area, termed the specific enevgy or energy 

 density, is given by 



^ -1-8 



(2-39) 



Wave energy flux is the rate at which energy is transmitted in the 

 direction of wave propagation across a vertical plane perpendicular to the 

 direction of wave advance and extending down the entire depth. The average 

 energy flux per unit wave crest width transmitted across a vertical plane 

 perpendicular to the direction of wave advance is 



P = EnC = EC 



g 

 Energy flux P is frequently called Wave power and 



(2-40) 



n = — 

 2 



1 + 



4i7d/L 



sinh(4Trd/L) 



If a vertical plane is taken other than perpendicular to the direction of wave 

 advance, P = E Cg sin ^, where (^ is the angle between the plane across which 

 the energy is being transmitted and the direction of wave advance. 



For deep and shallow water, equation (2-40) becomes 



P = — E C (deep water) 

 o 2 o o 



(2-41) 



P = EC = EC (shallow water) 

 g 



(2-42) 



An energy balance for a region through which waves are passing will reveal 

 that, for steady state, the amount of energy entering the region will equal 

 amount leaving the region provided no energy is added or removed from the 

 system. Therefore, when the waves are moving so that their crests are 

 parallel to the bottom contours. 



or since 



EnC = EnC 

 o o o 



n = — 

 o 2 



- E C = EnC 

 2 o o 



(2-43) 



2-26 



