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Título del libro: Asme 2015 13th International Conference On Nanochannels, Microchannels, And Minichannels, Icnmm 2015, Collocated With The Asme 2015 International Technical Conference And Exhibition On Packaging And Integration Of Electronic And Photonic Microsystems
Título del capítulo: EFFECT OF HYDRODYNAMIC SLIPPAGE ON OSCILLATING ELECTROOSMOTIC FLOWS IN INFINITELY EXTENDED MICROCAPILLARY

Autores UNAM:
FEDERICO MENDEZ LAVIELLE;

Autores externos:

Idioma:
Inglés

Año de publicación:
2015

Palabras clave:

Boltzmann equation; Diffusion in liquids; Electric fields; Electroosmosis; Hydrophobicity; Microchannels; Microfluidics; Microsystems; Nonlinear equations; Poisson equation; Strouhal number; Velocity; Zeta potential; Dimensionless frequency; Dimensionless parameters; Electrical potential; Electrokinetic potentials; Hydrodynamic slippage; No-slip boundary conditions; Nonlinear poisson-boltzmann equation; Time-dependent electric field; Oscillating flow

Resumen:

In this work we conduct a numerical analysis of the time periodic electroosmotic flow in a cylindrical microcapillary, whose wall is considered hydrophobic. The fluid motion is driven by the sudden imposition of a time-dependent electric field. The electrical potential is obtained by solving the nonlinear Poisson Boltzmann equation for high zeta potential, under the assumption that the electrokinetic potential is not affected by the oscillatory external field. In addition, we neglect the channel entry and exit effects, in such manner that the flow is fully developed. The governing equations are nondimensionalized, and the solution is obtained as a function of three dimensionless parameters: the ratio of the Navier slip length to the radius of the microcapillary delta; R-w, which is the dimensionless frequency for the flow or Strouhal number and measures the competition between the diffusion time to the time scale associated to the frequency of the oscillatory electric field; and (kappa) over bar, which represents the ratio of the radius of the microcapillary to the Debye length. The principal results show that using slippage, the bulk velocity increases for increasing values of delta. For the values of the dimensionless parameters used in this analysis, by using hydrophobic walls, the bulk velocity can be increased in about 20% in comparison with the case of no-slip boundary condition. On the other hand, the dimensionless frequency for the flow or Strouhal number plays a fundamental role in determining the motion of the fluid. For R-w << 1, the dissipation is found in resonance with the frequency of the oscillatory electric field. For R-w >> 1, the dissipation is not in phase with the frequency and, therefore, the velocity in the center of the microcapillary, in some cases, is almost null, and the maximum value of the velocity is near to the microcapillary wall.

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