An asymmetric turbulent fluid flow induced by rectangular ribbed surface roughness.

Abstract

The present thesis presents a theoretical as well as experimental investigation of fully developed turbulent fluid flow in partially roughened surfaces channel. The fluid properties wer assumed to be constant throughout the analysis. In the theoretical study of the problem the momentum integral method together with a turbulence model based on Prandtl's mixing length theory is adopted. The closure of the equations with one empirical constant was not possible and its was required to use empirical functions for the parameters describing the maximum velocity and zero shear stress points. The mean flow parameters of interests were given due considerations in the investigation. The experimental study involves the measurements of mean and turbulent characteristics of the flow in a partially roughened surfaced channel. The asymmetric flow between parallel planes was developed by roughening one of the planes with rectangular ribs while the other was left smooth. The most important parameters in the analysis are the locations of zero shear stress and maximum mean velocity points, since they are the main experimental inputs used in the prediction of mean flow parameters. The positions of the zero shear and maximum velocity points deviate more from the centre line of the channel towards the smooth wall for a lower roughness density as well as for increased Reynolds numbers corresponding to the same channel width.