Simulation of particle–vortex interactions in the modified chemical vapor deposition process

A computational fluid dynamics model is developed to examine deposition trends in the modified chemical vapor deposition (MCVD) process used in the fabrication of silica optical fibers. The model predicts the flow-field in a rotating tube and the location of the reaction zone. Silica particles generated in this zone are treated as being injected into the fluid dynamic system at this point and their trajectories calculated, taking into account drag and thermophoretic forces. The presence of double vortices in the flow was shown to play an important role in the determination of the particle deposition flux on the wall of the substrate tube, with the tangential velocity in the vortex zones responsible for particles being dragged away from the wall.