Thermophoretic Motion of a Spherical Aerosol Particle in a Cylindrical Pore

The thermophoretic motion of a spherical aerosol particle in a cylindrical pore, with the ambient temperature gradient imposed parallel with the pore direction, is investigated. Both particle and pore surfaces can have frictional and thermal slip, and discontinuity in temperature fields across both surfaces is allowed. The relevant boundary value problem is solved with a truncated-domain boundary collocation method. It is found that the thermo-osmotic flow of the surrounding fluid caused by the thermal slippage of the pore wall plays a dominant role in determining the thermophoretic motion of the particle. This thermo-osmotic flow is directed toward the hotter region and thus leads to a toward-hot-region thermophoretic motion of the particle, which is opposite to the usual toward-cold-region particle thermophoretic motion. The effect of this thermo-osmotic flow toward particle thermophoretic motion is quite different for the particle in a closed cavity situation. For the particle in a closed cavity scenario, the thermo-osmotic flow is toward the hotter region along the cavity wall, but has to circulate back in the middle of the cavity and thus helps to push the particle toward colder region.