Engineering method of calculation hydraulic drag coefficient and velocity profile for an arbitrary sand roughness of the pipe wall
The analysis of engineering methods of calculation of hydraulic drag coefficients in a circular tube and the velocity profile showed that most fully developed of calculation methods when flowing along a hydraulically smooth surface and under flow conditions with a full manifestation of sand roughness. All the methods of calculation of the flow in the transitional regime aimed at pairing the calculated dependences for hydraulically smooth and extremely rough surfaces. The resulting calculated dependencies are not taken into account, observed in the experiments, the minimum value of hydraulic drag coefficient, magnitude of which depended on the Reynolds number and relative roughness of the surface. In this paper, based on analysis of known experimental data I. Nikuradsen change the second constant of turbulence in the transitional regime, the proposed the empirical dependence, the use of which allows for enough good agreement with experimental data, including in the field of the minimum value of the hydraulic drag coefficient. On the basis of the proposed engineering method of calculation of hydraulic drag coefficient are obtained calculation correlation, allowing to define the velocity profile at an arbitrary roughness of the pipe wall.