Do the zones with negative eddy viscosity in longitudinally homogeneous turbulent flows exist?

The article explains the experimental data and confirms the presence of a thin wall layer with contragradient flow in longitudinally homogeneous turbulent flows. Review of opinions about the possibility of existence of zones with negative turbulent viscosity in the longitudinally homogeneous turbulent flows is given. There were obtained criteria, which make it easy to identify the areas with negative turbulent viscosity using empirical formulas. Application of the proposed criteria to the most noted empirical formulas revealed the record of the estimated area. Engaging with the same purpose of the most accurate experimental data has led to a positive result that allows drawing a definite conclusion about the existence of the zone with negative turbulent viscosity near the solid boundaries of longitudinally homogeneous flows.