Hydraulic resistance of an annular channel with a rectangular roughness on the wall

Abstract

This paper provides a brief overview of approaches to calculating the hydraulic resistance coefficient of a channel with rough walls and describes their advantages and disadvantages. One of the most popular engineering approaches is based on integral characteristics. By the influence of roughness, the logarithmic velocity profile changes, which is fully described by the second constant. It determines the interaction of a turbulent flow with a rough wall. Its numerical value depends on a large number of factors, such as geometry of the roughness protrusion, the dimensionless height of the protrusion, its shape, angle of attack, and so on. Getting a generalized dependence of this kind is an actual task of rough channel hydraulics. In this paper, the second constant of the logarithmic velocity profile is numerically calculated using turbulence models. A symmetric model of a developed turbulent flow in an annular channel with a rectangular roughness on the wall is implemented. Roughness was applied to the surface of the rod, the inner surface of the pipe was smooth. The result of numerical simulation was the obtained velocity profile, which was used to determine the numerical value of the second constant. The obtained results are satisfactory agreement with the experimental data.