Abstract

In this paper, we address the modeling of a complex glass forming process. The aim of the process is the production of rods and tubes with very tight specification of diameter and wall thickness. Modeling this process via simulations has two key benefits: (1) It provides deep insights into aspects that are inaccessible to available measurements. This allows, e.g., to better cope with real world disturbances, such as asymmetries of the furnace. (2) Advanced control strategies can be developed through experimentation and verification with the simulation model. We implement the glass formation process in terms of fluid dynamics (CFD), modeling the glass body as a fluid domain bounded by free surfaces including surface tension. The evolving shape is then calculated via interface tracking in conjunction with Stokes flow, where the melting of the glass is modeled by a viscosity with fitted temperature dependence. In our paper/presentation, we present the general setup of the model (which is implemented in COMSOL Multiphysics). A crucial issue is the accurate modeling of the radiative heating of the glass body as well as the heat transfer throughout the glass. We present different approaches to implement a radiation model, specifically the Rosseland and P1 approximations as well as variants of these approaches. For the heat exchange between oven and glass, we use a Surface-to-Surface (S2S) interface. Unfortunately, this does not account for the radiation penetrating the glass. We show how, as a practical solution, the incoming surface radiation can be coupled as a boundary source to a Radiation in Participating Media (RPM) interface. As a result, the temperature distribution in the glass becomes more realistic. We show some simulation results, which illustrate the problem as well as the improvements regarding the radiative heat transfer. We will present some applications demonstrating the quality and realism of the model.