Российский электрохимический журнал
The eddy viscosity and the eddy diffusivity are calculated for the viscous sublayer in turbulent flow near a solid surface by using Fourier transforms of a spectral element of the velocity profiles, the pressure, and the concentration. The different spectral elements are assumed to behave independently of each other in this region, and the magnitudes are plotted as functions of distance from the wall. The tangential velocity profiles show a slope of unity on log–log plots against distance y from the wall, while the normal component shows a slope of 2. The concentration profiles generally show a slope of unity except near the outer limit of the viscous sublayer. There is also a dependence on the value of the Schmidt number as well as the concentration fluctuation assumed to prevail at a distance of δ0 at the outer limit of the viscous sublayer. When the normal velocity fluctuation is correlated with either the streamwise velocity fluctuation or with the concentration fluctuation, one infers a slope for the eddy viscosity or the eddy diffusivity of 3. The eddy diffusivity shows more structure than the eddy viscosity and can differ substantially from the latter in the depths of the viscous sublayer.
- Department of Chemical and Biomolecular Engineering, University of California, 94720-1462, Berkeley, California, USA John Newman
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