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 (</=3tau(-1)). In addition to the two colloidal forces, the deposition process was also investigated in the presence of gravity and with a vertically applied electrical force. With these two external forces, the deposition becomes a two-dimensional (2D) boundary value problem for which a numerical solution was achieved using the implicit Crank-Nicolson method. Their effects on the 2D deposition process were studied.
Gu
Yongan
Y
Faculty of Engineering, University of Regina, Regina, Saskatchewan, S4S 0A2, Canada.
Li
Dongqing
D