APPENDIX C 

 DETERMINATION OF A*, B* AND 7| 



The method used for the determination of A*, B* and T\ has been 

 outlined in section 5 of the text. What we intend to do here is to 

 describe the experimental procedure used in connection with this method. 



The same flume which has already been described in previous sec- 

 tions was used, but with some slight modifications. The method called 

 for actual measurement of the quantity q B . By definition q B is the rate 

 at which sediment near the bed crosses a section of unit width positioned 

 perpendicular to the wave propagation. 



,g^<vaore««K>Mfr«ft<K^ 



Our experimental procedure was based on the proposition that the flow 

 field and consequently the magnitude of q R when the bed is fixed and the 

 boundary-layer flow is caused by a surface wave are the same as when the 

 bed is oscillating with a simple harmonic motion while the water surface 

 is at rest. The validity of this argument will be discussed later but 

 for the time being let us assume that it is correct. The oscillating 

 plate had to be modified so that measurement of q B could be made possible 

 The plan view and longitudinal section of the modified plate is shown in 

 the sketch below 



Tin — FF — ■ — — ~~-*~-~- * wv™-~*™r~~~™~*T~~M~^u*X r 



The procedure is self-explanatory. The space between the trays was 

 filled with loose sand of a given size. The plate then was set into 

 motion and after the completion of a number of periods it was stopped, 

 and the amount of sand collected in the middle tray was removed and 

 measured. A wire screen was placed on top of the trays so as to be 

 flush with the rest of the sandy bed to achieve uniform roughness 



C-l 



