Abstract
The investigation is a first approach to the problem of turbulent diffusion from a finite rectangular lake. A formal solution in terms of Mathieu functions is obtained for the problem of vapour distribution above and down-wind of the lake on the basis of an assumed law of lateral diffusivity. The air-stream is assumed to be fully turbulent and directed parallel to the longitudinal length of the lake. The application of the formal solution to special cases awaits the complete tabulation of Mathieu functions.