EXPERIMENTAL AND NUMERICAL ASSESSMENT OF THE INFLUENCE OF SPEED PROFILE PARAMETERS ON HYDRAULIC RESISTANCE IN SMOOTH AND ROUGH PRESSURE PIPELINES

The article analyzes the relationship between the logarithmic velocity profile parameters of turbulent flow in smooth and artificially rough pressure pipelines—the Karman parameter κ—and the free terms C1 and C2 with the hydraulic resistance coefficient λ. Empirical relationships based on the regression processing of Nikuradze's experimental profiles have been systematized, and their mathematical interdependence and application limits have been clarified. For smooth pipes, the dependence of κ and C1 on λ and the Reynolds number, the implicit resistance equation obtained by integrating the velocity profile, and the classical Nikuradze and Blazius dependencies were compared. It is shown that the interpretation of κ and C2 as a strictly monotonic function is limited due to the scattered nature of the experimental points along the rough pipes. To verify the results in the ANSYS Fluent environment, a numerical experimental methodology was developed, including geometry, a grid, a turbulence model, wall roughness, and evaluation criteria. Calculative analysis showed the need to evaluate the velocity profile parameters not as universal constants, but as effective parameters determined within the range of the flow under study.