Electroosmotic Fluid Motion and Late-Time Solute Transort for Large Zeta Potentials

摘要

Analytical and numerical methods are employed t o determine the electrtic potential, fluid velocity, and late-time slute distributio for electroosmotic flw in a tube and channel at #zeta# potentials tat are not necessarily small. The electric potential and fluid velocity are in general obatied by numerical means. In addiution, new anaytical solutions are presented for the velocity in a tube and chanel in the extremes of large and small Debye layer thickness. The electroosmotidc fluid velocity is used to analyze latetime transport of a neutral nonreacting xolute. Zero- and first-order solutions describing axial variatio of the solute concentration are determined analytically. The resulting expressions contain eigenvalues representing the dispersio and skewness of the axial concentration profiles. These eignenvalues and the functions describing transverse variation of the concentration field zre determined numerically using a shooting technique. Results are presented fro both tube and channel geometries over a wide range of the normalized Debye layer thickness and #zeta# potential. Simple analytical approximations to the eigenvalues are also prvided for the limiting cases of large and small values of the Deyby layer thickness.