Influence of three-dimensional wall roughness on the laminar flow in microtube

The regular perturbation method is introduced to investigate the influences of three-dimensional wall roughness on the laminar flow in microtube. Rough wall surface is modeled by two-dimensional simple harmonic function whose axial and azimuthal wavenumbers are alterable. Under this rough wall model, a set of coupled leading-order and first-order perturbation equations are obtained and computed iteratively. The numerical results show that flow in microtubes are more complex than those in macrotubes; pressure drops are about 0-65% higher than that of Hagen-Poiseuille flow on condition that the relative roughness increases from 0 to 0.05 and the wavenumbers of wall rough function range between 0 and 30; there exists apparent fluctuations in flow fields. Analysis shows that the effects of roughness on the flow pattern is distinct from those on the friction factor. (c) 2006 Elsevier Inc. All rights reserved.