The construction of the turbulence phenomenological theory in a liquid with drug reducing additives

Abstract

In the paper, the question of the construction of the turbulence phenomenological theory in liquids with small drag reducing additives (DRA) is considered. The thesis is put forward that the phenomenological theory is relevant for practical needs, since it determines the parameters of the phenomenon under consideration without using in detail the mechanisms that determine its effect. These mechanisms, despite many years of intensive research to date, remain either unknown or not fully understood. It is argued that different DRAs act differently on shear turbulence in pipes and channels and therefore change the integral characteristics of turbulent flow differently. Some DRAs act only on narrow near-wall regions of the flow, without changing the turbulent viscosity in the flow core, while others DRAs act in the entire volume of the turbulent flow, and significantly change the turbulent viscosity. The first type of DRAs form a turbulent flow by changing the boundary conditions in known models without changing the model coefficients. The second type of DRAs changes both the boundary conditions and the coefficients of the model itself. It is shown that the modified theory (model) of Karman shear turbulence is equally suitable for describing the turbulent fluid flow with DRAs of the first and second types. The universal resistance equation resulting from this model, with experimentally determined transfer coefficients, allows calculating the hydraulic resistance coefficient depending on the properties of the used DRAs.