Electroosmotic flow in microchannels

The electroosmotic flow induced by an applied electrostatic potential field through microchannels between two parallel plates and a 90 degrees bend is analyzed in this work. A nonlinear, two-dimensional Poisson-Boltzmann equa tion governing the electrical double-layer field and the Laplace equation g overning the electrostatic field distribution in microchannels are numerica lly solved using a finite-difference method. A body force caused by the int eraction between the electrical double-layer field and the applied electros tatic field is included in the full Navier-Stokes equations. The effects of the electrical double-layer field and the applied electrostatic field on t he fluid velocity distribution, pressure drop, and skin friction are discus sed. A small pressure drop along the parallel plates is detected, although it is always neglected in the literature. Pressure is not a constant across the channel height. The axial velocity profile is no longer flat across th e channel height when the Reynolds number is large. A separation bubble is detected near the 90 degrees junction when the Reynolds number is large, (C ) 2001 Academic Press.