Title: Roughness effects in turbulent channel flow

Authors: Alireza Ashrafian, Helge I. Andersson

Addresses: Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Department of Process Technology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway ' Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491 Trondheim, Norway

Abstract: DNS of turbulent channel flow at Re_τ = 400 is performed. Both walls are roughened by square rods. The height of the roughness elements is smaller by a factor of 3 than in all earlier computer simulations. The turbulent flow is in the upper end of the transitional regime, where viscous drag is negligible. Substantial changes in all turbulence statistics are only seen within the roughness sublayer, where detailed information is provided. Hence, smooth-wall scaling applies in the outer layer. The anomalous turbulence features observed in the near-wall region are due to the blocking effect of the roughness elements and the intense shear layers emanating from the rods.

Keywords: surface roughness; transverse ribs; DNS; direct numerical simulation; turbulence; channel flow; CFD; computational fluid dynamics; turbulent flows.

DOI: 10.1504/PCFD.2006.009478

Progress in Computational Fluid Dynamics, An International Journal, 2006 Vol.6 No.1/2/3, pp.1 - 20

Published online: 05 Apr 2006 *

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