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.