T.M. No. 45 - October 1954 



Modification of Wave Height Due to Bottom Friction, Percolation and 

 Refraction by C. L. Bretsciineider and R. 0. Reid 



A report on a theoretical investigation of the transformation 

 (including energy loss) of waves in shallow water by bottom friction, 

 percolation, refraction, and shoaling. Using dissipation functions 

 introduced by Putnam and Johnson (1949), derived from the theory of 

 progressive waves of small amplitude, a general solution of the 

 steady state energy equation is obtained. For the case of a bottom 

 of uniform slope and the case of a bottom of constant depth, the 

 solutions are presented in convenient graphical form, making it 

 possible to obtain the reduction factor due to friction or perco- 

 lation for any bottom slope, depth, initial wave height or period 

 if the friction factor and permeability coefficient for the bottom 

 are known. An example involving refraction is presented. 



T.M. No. 46 - September 1954 



Field Investigations of Wave Energy Loss in Shallow Water Ocean 

 Waves by C. L. Bretschneider 



Results of a field investigation of loss of wave energy from 

 ocean waves passing through shallow coastal waters in the Gulf of 

 Mexico off the coast of Louisiana and Texas are reported. Results 

 from field observations are compared with existing theoretical 

 treatments for losses due to bottom friction. As apparent friction 

 factors determined appeared to be relatively high, energy losses 

 due to oscil latory adjustment of the bottom to variation in wave 

 pressure caused by the passage of surface waves are also considered. 

 Analysis of recorded wave data for this project are included for com- 

 parison with previously published data on statistical distribution 

 of wave heights in ocean wave trains. 



T.M. No. 47 - July 1954 



Stabi I ity of Osci I latory Laminar Flow Along a Wa I I by Huon Li 



Results are reported for a laboratory study of the transition 

 from laminar to turbulent flow in an oscillatory boundary layer 

 near the solid bottom caused by a surface wave. For experimental 

 convenience, observations were made at a plate oscillating in still 

 water. The relationships between the two flow conditions are dis- 

 cussed, and experimental results including observations for both 

 smooth and rough surfaces are given. 



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