Curvature-induced secondary microflow motion in steady electro-osmotic transport with hydrodynamic slippage effect
- Curvature-induced secondary microflow motion in steady electro-osmotic transport with hydrodynamic slippage effect
- 임진명; 전명석
- microfluidics; electro-osmotic flow; secondary flow; hydrodynamic slip; electrokinetics; vorticity; Dean flow
- Issue Date
- Physics of fluids
- VOL 23, NO 10, 102004-1-102004-10
- In order to exactly understand the curvature-induced secondary flow motion, the steady electroosmotic
flow (EOF) is investigated by applying the full Poisson-Boltzmann/Navier-Stokes equations
in a whole domain of the rectangular microchannel. The momentum equation is solved with
the continuity equation as the pressure-velocity coupling achieves convergence by employing the
advanced algorithm, and generalized Navier’s slip boundary conditions are applied at the hydrophobic
curved surface. Two kinds of channels widely used for lab-on-chips are explored with the
glass channel and the heterogeneous channel consisting of glass and hydrophobic polydimethylsiloxane,
spanning thin to thick electric double layer (EDL) problem. According to a sufficiently low
Dean number, an inward skewness in the streamwise velocity profile is observed at the turn. With
increasing EDL thickness, the electrokinetic effect gets higher contribution in the velocity profile.
Simulation results regarding the variations of streamwise velocity depending on the electrokinetic
parameters and hydrodynamic fluid slippage are qualitatively consistent with the predictions documented
in the literature. Secondary flows arise due to a mismatch of streamline velocity between
fluid in the channel center and near-wall regions. Strengthened secondary flow results from increasing
the EDL thickness and the contribution of fluid inertia (i.e., electric field and channel curvature),
providing a scaling relation with the same slope. Comparing with and between the cases
enables us to identify the optimum selection in applications of curved channel for enhanced EOF
and stronger secondary motion relevant to the mixing effect.
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