| The complete thermal transport process during fiber drawing process has been numerically and analytically investigated. The transport process has been studied for two distinct type of problems, namely the forced convective cooling of optical fiber, and the transport during necking of glass in a high-temperature environment.; The forced convective cooling of optical fiber coming out of a high temperature furnace is first considered. Conjugate transport has been considered by solving transient, elliptic set of governing equations in fluid and solid. Effect of different physical and process variables on the temperature and flow field has been studied in details. The relative importance of buoyancy for similar cooling process in other material processing applications has also been investigated.; The convective and radiative transport in the neck-down region of optical fiber during furnace drawing have been rigorously modeled. Due to the arbitrariness of necking shape, an appropriate coordinate transformations have been used for both glass and external fluid to convert the actual physical domains to a computationally convenient rectangular ones. A highly non-linear coupled set of governing equations is numerically solved using a modified false transient method. The dependence of the temperature and flow field in the necking region and the external fluid on different operating conditions has been studied in details. An analytical and numerical approach have been developed for the generation of neck-down profile during high-temperature drawing. The procedure is based on an iterative correction of radius based on force balance at the surface. The neck-down profile has been obtained for a wide range of physical and process variables. The numerical scheme has been widely validated based on consistency and comparison with experimental data. Finally, some practical situations that arise in fiber drawing have been considered. Based on a study of feasibility of drawing under different operating conditions and considerations based on defect concentrations and stability, a suggestion is made about optimal combination of design parameters. |
