ВПЛИВ ПАРАМЕТРІВ ПРИМЕЖОВОГО ШАРУ НА ГІДРАВЛІЧНІ ОПОРИ У ТРУБОПРОВОДАХ

The suitability of the previously obtained analytical dependence for determining the coefficients of hydraulic friction of pipelines with different types and values of roughness is confirmed. It is established that in a wide range of turbulent regimes in pipelines, the coefficients of hydraulic friction depend on two determining parameters: the hydraulic thickness of the boundary layer and the coefficient of proportionality of turbulent pulsations to averaged velocities. At the same time, the change in the value of the hydraulic thickness of the boundary layer from the influencing factors has a determining value on the type and nature of the dependence of the coefficients of hydraulic friction on the flow regimes. It is shown that the hydraulic thickness of the boundary layer depends on the molecular viscosity of the turbulent fluid flow and the relative hydraulic roughness of the pipelines, which in turn depend on the flow regimes and the state of the inner surface of the pipelines. The main influencing factors on it are the values of Reynolds numbers, coefficients of hydraulic friction and hydraulic roughness of pipes. Considering that the roughness of pipe walls depends on the types of roughness (smooth, sharp-topped, wavy, industrial depending on the method of pipe manufacturing, sandy), the sizes of the protrusions themselves, their shape and the methods of their location on the pipe walls (uniform, with different types of profiles, uneven in area, with significant rarely located tubercles of various shapes, etc.), a semi-empirical dependence has been proposed for determining the hydraulic thickness of the boundary layer. Its validity is confirmed by the correspondence to experimental data on determining the coefficients of hydraulic friction of pipelines of different materials, diameters and types of roughness in a wide range of Reynolds numbers (from 4 10³ to 10⁷). Based on the processing of experimental data, numerical values of parameters for calculating the hydraulic thicknesses of the boundary layer and the coefficients of hydraulic friction of pipelines are determined. The accuracy of calculations using a simplified version of the proposed dependencies for determining the coefficients of hydraulic friction is estimated.