Computational Study of Convective Transport in a Coating Applicator for a Non-Newtonian Fluid

Abstract

Convective transport in an optical fiber coating applicator and die system has been simulated for a non-Newtonian fluid. Low-density polyethylene (LDPE) is employed for the numerical analysis, though ultraviolet (UV) curable acrylates are more commonly used, because of a lack of property information for acrylates and similar behavior of these two materials. The equations governing fluid flow and heat transfer are transformed to obtain flow in a cylindrical domain. A numerical scheme similar to the SIMPLE algorithm is developed and employed with a nonuniform grid. Variable fluid properties are employed because of the strong dependence of these on the temperature. In contrast to the isothermal case, streamlines for the non-Newtonian fluid are found to be quite different for various fiber speeds. The temperature level in the applicator is much higher for the Newtonian case, due to the larger fluid viscosity and associated viscous dissipation. The shear near the fiber is found to be lower for the Newtonian fluid. As expected, the effects become larger with increasing fiber speed. A fairly high temperature rise is observed in the die, regardless of fiber speed. This study focuses on the computational modeling of non-Newtonian effects during the coating process, and several interesting and important features, as compared to the Newtonian case, are observed.

The authors acknowlege support by the National Science Foundation under grant no. CTS-0119356 for this work, and the discussions with Prof. C. E. Polymeropoulos on fiber coating.