Abstract
Simulation of fluid flow and friction in a circular shaped ribbed microchannel using the Lattice Boltzmann Method (LBM) has been studied in the present paper. In micro-flows, the local density variation is still relatively small, but the total density changes, therefore, in order to account this density variation and its effect on the kinematic viscosity ν, a new relaxation time is used. The roughness geometry is modeled as a series of circular riblets with a relative roughness (ɛ) height up to a maximum 10% of the channel height. To analyze the roughness effects, the friction coefficients in terms of Poiseuille number, Pn, has been discussed. Actually, the friction factor properties of riblets, depending on the particular geometry, are analyzed in the slip flow regime at Knudsen number, Kn, ranging from 0.01 to 0.10 with other controlling parameters. The velocity profiles in terms streamlines near the riblets are demonstrated to be responsible for the roughness effect. Finally the results have been compared with previous published works and it is found to be in good agreement.