Deposition of spherical particles onto cylindrical solid surfaces. I. Numerical simulations

In this article, analytical and numerical solutions are given for the deposition of spherical particles onto cylindrical solid surfaces. If only the retarded van der Waals (vdW) force and the electrical double-layer (EDL) force between the spherical particle and the cylindrical surface are considered, such a deposition process is governed by a one-dimensional (1D) mass transfer equation for which both analytical and numerical solutions are obtained. A parametric study was conducted to examine the effects of these two colloidal forces on the deposition process. The numerical results show that the attractive vdW force, as represented by the dimensionless adhesion number A(d), is a necessary condition for deposition to occur. However, it affects only the drop number concentration distribution and, to a limited extent, the mass transfer rate. In general, the 1D deposition process is dominated by the EDL force, as represented by the dimensionless EDL parameter Dl and the reduced radius tau=kappaa of the spherical drop. It is noted that tau plays a key role in determining the effect of the EDL force on the mass transfer rate since an appreciable EDL force exists only within small separation distances (