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Measurements of the effect of molecular diffusivity in turbulent diffusion

Published online by Cambridge University Press:  28 March 2006

William R. Mickelsen
William R. Mickelsen
Affiliation:
National Aeronautics and Space Administration, Lewis Research Center, Cleveland, Ohio, U.S.A.
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Abstract

Townsend (1954) has shown that turbulent vorticity may rotate and strain a diffusion wake, thereby increasing the contribution of molecular diffusion to the total mean dispersion over short diffusion times. To test whether any such effect occurs at longer diffusion times, the lateral dispersion of both helium and of carbon dioxide in air were measured downstream from a continuous point source in the turbulence produced by a grid in a wind tunnel. The data show that, for long diffusion times, accelerated molecular diffusion is negligible, so that molecular diffusion makes only an independent contribution to the total dispersion.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 7 , Issue 3 , March 1960 , pp. 397 - 400
Copyright
© 1960 Cambridge University Press

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References

Batchelor, G. K. 1952 Proc. Camb. Phil. Soc. 48, 345.
Batchelor, G. K. & Townsend, A. A. 1956 Article in Surveys in Mechanics, p. 352. Cambridge University Press.
Mickelsen, W. R. 1955 Nat. Adv. Comm. Aero. Tech. Note 3570.
Taylor, G. I. 1922 Proc. Lond. Math. Soc. (2), 20, 196.
Townsend, A. A. 1954 Proc. Roy. Soc. A, 224, 487.