Axisymmetric and non-axisymmetric turbulent diffusion in a plain circular tube at high Schmidt number

Abstract

Measurements were made of the radial and tangential eddy diffusivities of mass in a fully developed turbulent flow in a plain circular tube for Schmidt numbers ranging from 760 to 1200 with Reynolds numbers ranging from 5230 to 23 550. The results, expressed as the ratio of the radial eddy diffusivity of mass to that of momentum and as the ratio of the tangential eddy diffusivity of mass to the radial, are found to be simple functions of non-dimensional radius. They are indistinguishable from some previous measurements at Prandtl and Schmidt numbers of about unity. This is in contrast with several theories of turbulent exchange which predict an effect of increasing Prandtl or Schmidt number on the ratios. It is concluded that both ratios are simple functions of non-dimensional radius and increasing Schmidt number and, probably, Prandtl number have no effect on them.