INTRODUCTION 



Three approaches have been made to the study of internal waves and 

 associated phenomena — theoretical analysis, model study, and field experiment. 

 This report discusses the results of the first two applied to the specific problem 

 of the diffusion of a solute between two discrete layers. The fluid model is pre- 

 pared by dissolving different amounts of solute in successive layers of fluid. 



THEORY 



Attention is restricted to a two-layer liquid system with combined thickness 

 I. Let the upper layer, of thickness h, initially be a pure solvent lying on a layer 

 of thickness (I — h) of solution having a concentration C . If the diffusion coeffi- 

 cient k can be taken as constant for concentrations ranging from to C e , the con- 

 centration satisfies the simple diffusion equation, subject to the appropriate initial 

 and boundary condition. This problem, as a special case of a more general treat- 

 ment, is treated in the appendix. The solution is 



e = ?l\ed(2±) - erf(^) + e4~) ~ «f(-^j (1) 



2 ( \vW/ V^feT/ WiktJ \/4ktl\ 



where erf stands for the error function, z is distance from surface, the absolute 

 value of the argument is used, and the sign of the term is changed if the argument 

 is negative. 



