Abstract
The modification of the fluid model to describe the turbulent flow is considered. We study the hydrodynamic instability, methods of description of turbulence, the problem of averaging and the energy balance of the turbulent fluid. Finally, we derive the Reynolds equation of motion.
Keywords: Eddy viscosity, Hydrodynamic instability, Laminar mode, Reynolds conditions, Reynolds equation, Reynolds number, Reynolds stress tensor, The averaging problem, Turbulence, Turbulent energy, Turbulent mode.