Collision efficiency of uncharged conducting spheres in a uniaxial compressional flow and an external electric field*

We study collisions of a pair of uncharged conducting spheres subject to a uniaxial compressional flow and an external electric field. The near-field asymptotic expression for the electric-field-induced attractive force between two spherical conductors can overcome the lubrication resistance leading to surface-to-surface in finite time. We demonstrate the role of the external electric field in the particle trajectories and estimate how the shear-induced collision efficiency depends on electric-field-induced forces. Because the continuum lubrication interactions are no longer valid when the suspending medium is a non-continuum gas, we include the non-continuum lubrication interactions in our analysis. We show how collision efficiencies vary with the particle size ratio, the Knudsen number, and the dimensionless parameters capturing the relative strengths of electric-field-induced and the van der Waals forces.