  We investigate experimentally phenomenon of turbulent thermal diffusion of
micron-size solid particles in an inhomogeneous convective turbulence forced by
one vertically-oriented oscillating grid in an air flow. This effect causes
formation of large-scale inhomogeneities in particle spatial distributions in a
temperature-stratified turbulence. We perform detailed comparisons of the
experimental results with those obtained in our previous experiments with an
inhomogeneous and anisotropic stably stratified turbulence produced by a one
oscillating grid in the air flow. Since the buoyancy increases the turbulent
kinetic energy for convective turbulence and decreases it for stably stratified
turbulence, the measured turbulent velocities for convective turbulence are
larger than those for stably stratified turbulence. This tendency is also seen
in the measured vertical integral turbulent length scales. Measurements of
temperature and particle number density spatial distributions show that
particles are accumulated in the vicinity of the minimum of the mean
temperature due to phenomenon of turbulent thermal diffusion. This effect is
observed in both, convective and stably stratified turbulence, where we find
the effective turbulent thermal diffusion coefficient for micron-size
particles. The obtained experimental results are in agreement with theoretical
predictions.
