SBIR Phase I: Modeling of Thermal Transport and its Interaction with Crystal Formation in Optical Fiber Drawing on Distributed Memory Machines

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This Small Business Innovation Research Phase I project is to develop and demonstrate a computational tool for detailed simulation of thermal transport in a optical fiber drawing process on distributed memory machines. The ZBLAN optical fibers may replace the existing silica optical fibers in the next century because they have broader spectrum and lower loss coefficient. However, the ZBLAN glass tends to crystallize during the drawing of optical fiber. The suppression of crystallization requires a clear understanding of thermal transport involving radiative heat transfer and two-phase flow with a curved free surface. In Phase I, the finite volume method (FVM) will be modified to simulate radiative heat transfer in the gas enclosure as well as inside the glass. The gas-glass interface is treated as an optically directional and reflecting surface. The full elliptic governing equations will be solved for both glass and external gas, which are coupled by the conjugate boundary conditions at the interface. The discretization of the physical domain will be carried out by the multizone adaptive grid generation (MAGG) technique. An efficient parallel algorithm will be developed and implemented in the solution procedure with message passing by the Message Passing Interface (MPI) library. A parallel algebraic multi-grid (AMG) solver will be developed to solve the discretized equations. The Phase I will demonstrate the high accuracy and efficiency of the proposed simulation tool for thermal transport process. In Phase II, the crystal formation model will be developed, and the coupling between thermal transport and crystal formation will be completed in the tool. The simulation tool to be developed will significantly benefit the optical fiber industry that requires a detailed understanding of multimode and highly coupled transport phenomena and their interactions with thermal induced defects. The potential applications include the design, optimization, and control of optical fiber drawing process and many other manufacturing and materials processing systems.Key Words: Optical Fiber Drawing, Radiative Heat Transfer, Parallel Computing.