Hydrodynamic and surface interaction forces on a particle in a pore

The interaction between a spherical particle in a pore near a constriction and the wall is calculated in order to understand the behavior of dispersions on their transport through a porous medium. A simplified geometry of the pore is assumed which permits, for a spherical particle: 1. (a) Analytical calculation of the London-van der Waals attraction; 2. (b) Calculation of electrostatic repulsion by numerical solution of the Poisson-Boltzmann equation and application of the Langmuir equation for the repulsive pressure; and 3. (c) Calculation of hydrodynamic interactions by numerical solution of the Navier-Stokes equation by means of a finite element method. The method permits solution of the Navier-Stokes equation, in the low Reynolds number range (e.g., Re = 5 × 10^-4), as long as the closest distance between the particle and the wall is at least 0.3 μm. The results indicate that under the conditions covered by the present calculations, for a stationary particle near a pore constriction, the hydrodynamic interactions by far predominate over colloid chemical interactions.