Abstract:
Motion of a charged particle inside an electrolyte lled uncharged channel is hindered
due to hydrodynamic e ect and electrokinetic e ects. Presence of an obstacle on
wall surface increases the drag force on the particle and reduces the particle velocity.
Flagellum like obstacle tends to shift the particle away from the center. When any
or both the particle and
agellum are charged di erent electrokinetic phenomena
like repulsion, relaxation, electrical double layer overlap a ect the drag force on the
particle. Electrostatic repulsion always force the particle away from the
agellum
if both the particle and
agellum are similarly charged and vice versa. Distortion
of electric double layer causes relaxation which always tends of increase the drag
force in
ow direction. Double layer overlap also a ects the drag by redistributing
the charge concentration. A nite element model consisting of Navier-Stokes, Pois-
son and Nernst-Plank equation has been developed to quantify the e ect of such
parameters on particle drag force. It is found that presence of
agellum hydrody-
namically tends to o center the particle at
agellum upstream and later brings it
back. Relaxation more prominently a ects electrical drag force than electrostatic
repulsion and increases the drag force on the stationary particle in
ow direction.
With the decrease of separation distance both the hydrodynamic and electrical drag
force increase. Solution concentration has signi cant e ect on the drag force. With
the increase of concentration electrical drag force increases signi cantly due to in-
creased surface charge on the particle surface resulting in higher total drag force.
Drag factor has been found to be higher for charged particle than uncharged one.
This excess drag is also increases with solution concentration.
