Diffusion of Matter in Wall Turbulent Flow : 4th Report, Local Similarity of Mean Concentration Field of the Plume from a Wall Point Source in Turbulent Pipe Flow

Abstract

The aim of this study is to find similar solutions of the ordinary differential equation for the suitably normalized function in order to describe the mean concentration distribution, the similarities of which were experimentally observed in the some region downstream of a wall point source plume in a turbulent pipe flow. Solutions of these equations are compared with experimental data, which were obtained in an almost fully-developed water turbulent pipe flow (Re_D=20000) that has been realized in a horizontal straight pipe of inner diameter 100 mm. It is found that these solutions show good agreement with experimental data, and the widths of similar profiles are strongly affected by the curvature of the boundary of the flow field. This is mainly caused by the diffusion term in a conservation equation for the mean concentration field. Also, the ordinary differential equation for the normalized mean concentration function in the case of a wall point source plume in a turbulent boundary layer on a flat plate is found to be a special case of the corresponding equation for a turbulent pipe flow.