IMPORTANCE OF DIFFUSION ALONG MEAN WIND DIRECTION FOR A GROUND-LEVEL CROSSWIND LINE SOURCE

A special case of a solution obtained earlier by Roberts in an unpublished paper is a solution considered by Bosanquet and Pearson (1936) of the problem of diffusion from a ground-level infinite line source into a turbulent flow of air moving perpendicular to the source. In the present paper the solution considered by Bosanquet and Pearson is extended to the case when the term representing diffusion in the direction of flow is taken into account. Like the eddy diffusivity in the vertical direction (z) in the earlier solution, the diffusivity in the direction (x) of the mean turbulent flow is assumed, in the present paper, to vary linearly with height above the ground. The functional dependence on z and x (but not, necessarily, the absolute magnitude) of the concentration predicted at points downwind of the source and sufficiently near the ground is the same as that in the solution considered by Bosanquet and Pearson; experimental results yield a value of a parameter occurring in the present solution which makes for near-equality in absolute magnitude, too, between the present solution and the earlier, in this range. © 1967.