Modeling of Surface-Fluid Electrokinetic Coupling on the Laminar Flow Friction Factor in Microtubes

The present work’s originality lies in the evidence of a non negligible effect of the fluid ions’ and co-ions’ interaction with the wall surface in a microtube. This study is based on the EDL theory (Electrical Double Layer) which is developed here for a circular geometry. High electrical surface potentials are taken into account for the present study; they induce the nonlinearity of the problem’s main equation (Poisson-Boltzmann equation). The electrical field is determined, then the velocity profile and finally the Poiseuille number. We show that even with the EDL effect taken into account, the Poiseuille number does not depend on the mean velocity. Our model agrees with the experimental results for high surface potentials (> 25 mV). This is found by comparing with experiments previously carried out with microtubes ranging from 530 to 50 μm.