Fluidized bed of fine grains (aerosuspension) is known to be used to separate a mixture of particles of different size and composition in gravity concentration of minerals.

The limits of the applicability of the concept of viscosity. In molecular physics, it is shown that the phenomena of diffusion, thermal conductivity, and internal friction in gases are based on a single mechanism - the transfer of mass, energy, and amount of motion from one gas layer to another by chaotically moving molecules. This commonality of the mechanism is manifested in the presence of a connection and mutual proportionality of the coefficients of diffusion, thermal conductivity and internal friction - viscosity...

Determination of the sizes of inclusions and the function of their size distribution in the mineral volume is an important task for practice. Since in the vast majority of minerals containing inclusions are opaque, it is not possible to experimentally measure the sizes of inclusions. Usually the sizes of inclusions cross-sections are measured on the slip, and by the picture on the slip we have to judge about the true sizes of inclusions in the mineral and about the size distribution of inclusions.

Free fall of spherical particles in a viscous fluid has been studied by many researchers in connection with mineral processing, chemical technology, metallurgy, etc. By changing the diameters of balls, density and viscosity of the fluid, it was possible to trace the motion of particles in the region of small and large values of the Reynolds and Archimedes criteria, i.e. in laminar, transitional and turbulent regimes.

In a number of branches of engineering - in gravitational concentration of minerals, some processes of chemical technology and others, we meet with the constricted motion of bodies in a medium with resistance. At constricted motion conditions of streamline and resistance forces depend on such factors as body dimensions, fluid properties, proximity of neighboring bodies or vessel walls, etc.