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DNS OF TURBULENT FLOW IN A ROD-ROUGHENED CHANNEL

Alireza Ashrafian
Department of Energy and Process Engineering, Norwegian University of Science and Technology N-7491 Trondheim. Norway

Helge I. Andersson
Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, Norway

Resumo

Turbulent flow in a channel with straight walls roughened by transverse rods is investigated using direct numerical simulation at Reynolds number based on the mean pressure-gradient, Re* = 400. Periodically arranged, two-dimensional, spanwise, square rods are introduced on both walls in a non-staggered configuration. The pitch-to-height ratio was 8, which corresponded to the so-called 'k-type' roughness and was operating in a transitional flow regime where both viscous and form drags are important. Numerical results were compared to the smooth wall channel flow simulation of Moser et al. (1999) at Reτ = 395. Effects of wall roughness on the turbulent flow field have been studied. The mean velocity profile, as expected, differs substantially from the profile on the smooth wall. Turbulence is substantially different in the near-wall region from that of a smooth wall. Differences are associated with a shear layer which is formed by flow separation.