Turbulent Thermal Diffusion

  Description

    We predicted theoretically a new phenomenon of turbulent thermal diffusion associated with turbulent transport of aerosols or gaseous admixtures. The essence of this phenomenon is the appearance of a nondiffusive mean flux of particles or gases in the direction of the mean heat flux which results in formation of large-scale inhomogeneities in the spatial distribution of aerosols or gases. The effect of turbulent thermal diffusion causes accumulation of aerosols or gases in regions of minimum mean temperature of the surrounding fluid. The effect of turbulent thermal diffusion is of great importance in various atmospheric and industrial turbulent flows, e.g., smog formation, fuel combustion and soot formation in internal combustion engines.     The existence of the phenomenon of turbulent thermal diffusion was validated in our laboratory experiments. In experiments turbulence was generated by two oscillating grids with two directions of the imposed vertical mean temperature gradient. We used Particle Image Velocimetry to determine the turbulent velocity field, and an Image Processing Technique based on an analysis of the intensity of Mie scattering to determine the spatial distribution of aerosols. Analysis of the intensity of laser light Mie scattering by aerosols showed that aerosols accumulate in the vicinity of the minimum mean temperature due to the effect of turbulent thermal diffusion.

  Experimental Results

  References