Thermophoretic motion of an aerosol particle in a non-concentric pore

Abstract

The thermophoretic motion of a spherical aerosol particle arbitrarily situated in a spherical pore is studied. The effect exerted by the boundary on the translational and rotational thermophoretic velocities of the particle is investigated by solving the relevant boundary value problem with a boundary collocation method. Variations in particle size, deviation of particle center from pore center, frictional slip coefficients of the particle and pore surfaces, and thermal conductivities of the particle and pore surfaces are studied. Both particle and pore surfaces can have frictional and thermal slip, and discontinuity in temperature field is allowed on both surfaces. Due to system symmetries, there exist only two independent scenarios for the present problem: one with the imposed ambient temperature gradient parallel to the line of centers between particle and pore (parallel case) and the other perpendicular to the line of centers (perpendicular case). It is found that only translational motion can be induced for the parallel case, while both translational and rotational motions occur for the perpendicular case. The thermo-osmotic flow induced by the thermal slip of the pore surface enhances the thermophoretic motion. The physical properties (thermal conductivity, slip coefficient, and temperature jump coefficient) of the particle are found to be more influential than those of the pore. The enhancing effect of particle or pore thermal conductivity reaches its saturation at the thermal conductivity value of about 100. Furthermore, the parallel normalized translational thermophoretic velocity is always greater than the perpendicular one, and the normalized rotational thermophoretic velocity correlates positively with the difference of the two translational velocities.