Two-dimensional asymmetric turbulent flow in ducts

An experimental and theoretical investigation is reported on the asymmetric, quasi-parallel flow of turbulent incompressible fluids. The experimental programme consisted of providing detailed measurements of mean and turbulent characteristics of the fully developed flow in a plane channel having one smooth wall, while the other was roughened by transverse square ribs. The dissimilar wall conditions imposed a strong asymmetry upon both mean and turbulent flow fields bringing into prominance several interating features that are concealed in the symmetric flow situations. The theoretical investigation concerned the provision of a procedure capably of accurate prediction of strongly asymmetric quasi-parallel flows. The research was concentrated upon the physical aspect of the problem, that is the establishment and testing of an approximate closed set of the transport equations, sufficient for the accurate description of the considered flows. Two physical models have been explored, both of which used the Spalding-Patankar numerical method for the solution of resulting equations. The first model, based upon the extension of Kolmogaa Prandtl eddy viscosity formula was tested in plane all-smooth and smooth-rough channels. It showed several deficiencies and was subsequently discarded. A second model was established that is described by a closed set of four partial differential equations for conservation of mean momentum, turbulent shear stress, turbulent kinetic energy and its clissipation. This model was extensively tested is several types of duct flows, wall boundary layers and quasi-parallel free flows. With a single set of empirical constants, the model yielded predictions of various flow properties which were in good agreement with experiments.Open acces