Hsu and Yu 



action or at x = 0. 



The total energy per unit of surface area E of a small- 

 amplitude, sinusoidal, progressive wave is 



If the energy corresponding to ag is Eg, Eq. (8) may be rewritten 

 as 



E = E„ exp [- -Ea kVpx] (9) 



° g P„ " 



The out-of-phase pressure component P is responsible for the energy 

 transfer from the air stream to the wave. Experimental results are 

 presented in the non-dimensional form 



',0 Wt - ^^ ""' 



where F is a non-dimensional fetch 



and 



F = — U, Px 

 I 



-3 



A=f2£fl-'\log e = l. 03X10 

 for p = 1 gm/cm^ and p =0,00118 gm/cm . 



Yf ^ 



III. LABORATORY INVESTIGATIONS 



3.1. Techniques of Simulation 



3.1.1. Moving wavy-boundary (steady- state) 



In attempts to verify Jeffreys' sheltering hypothesis, Stanton, 

 et al. [ 1932] , Motzfeld [1937] , Thijsse [ 1951] , and Larras and 

 Claris [ I960] measured pressure distributions over stationary, 

 solid, and two-dimensional sinusoidal boundaries in either a wind 

 tunnel or a water channel. In the light of the critical-layer mecha- 

 nism proposed by Miles, these stationary wavy-boundary experiments 



14 



