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Center for Nonlinear Studies |
There is a growing trend in nuclear reactor simulation to consider multiphysics problems. For example, analysts are interested in coupled flow, heat transfer and neutronics in reactor analysis. Many of the coupling efforts to date have been simple "code coupling" or first-order operator splitting, often referred to as loose coupling. While these approaches can produce answers, they usually leave questions of accuracy and stability unanswered. Additionally, the different physics often reside on separate grids which are coupled via simple interpolation, again leaving open questions of stability and accuracy. The simulation tool, PRONGHORN, takes advantages of the Multiphysics Object-Oriented Simulation Environment (MOOSE) library, and is capable of solving multidimensional thermal-fluid and neutronics problems implicitly in parallel. Expensive Jacobian matrix formation is alleviated by the Jacobian-free Newton-Krylov method, and physics-based preconditioning is applied to improve the convergence.In this presentation we will first discuss some algorithmic issues related to JFNK and physics-based preconditioning. Then we discuss MOOSE framework and application code PRONGHORN.