DEVELOPMENT OF THE HIFI EXTENDED MHD CODE AND APPLICATION TO INNOVATIVE CONFINEMENT CONCEPTS
Author: Alan H. Glasser
Requested Type: Poster Only
Submitted: 2011-06-16 10:42:36
University of Washington
3833 NE 155th St.
Lake Forest Park, WA 98155
We present an overview of the development of the HiFi extended MHD code and its appliation to the modeling of Innovative Confinement Concepts. HiFi, written in Fortran 95, uses advanced computational methods to achieve speed, accuracy, flexibility, ease of use, and state-of-the-art visualization. Spatial discretization uses high-order spectral elements on a logically rectangular 2D or 3D grid block, with a curvilinear mapping from logical to physical coordinates, facilitating efficient treatment of multiple length scales. It can treat an unstructured array of structured grid blocks, allowing discretization of complex geometry and avoiding regions of distorted grid such as polar axes. A semi-automated interface to CAD drawings is provided by the CUBIT code. Time discretization uses a fully implicit Crank-Nicolson time step, facilitating efficient treatment of multiple time scales, requiring solution of large sparse matrices on distributed memory supercomputers. This makes extensive use of the PETSc, Hypre, and SuperLU public-domain libraries, developed with the support of DOE/OASCR, with the benefit of much assistance from their development teams. The solution procedure is built from a hierarchy of methods: Matrix-Free Newton-Krylov on the full nonlinear systems, preconditioned by physics-based preconditioning and static condensation, then using Conjugate Gradients or GMRES to solve the reduced linear systems, preconditioned by Hypre/BoomerAMG or additive Schwarz overlap with core-wise SuperLU. Computational methods are compiled into a solver library, with the physics and geometry of each application specified in a much smaller module which links to that library. This module provides interior equations in flux-source form, as well as general, physically realistic boundary conditions, initial conditions, grid specification, facilitating the treatment of a wide range of appliations, including both ICCs and Tokamaks. Visualization uses the VisIt library with data files written in HDF5. The code is available for download and use, with limited support from the developers. We will present details of the development and testing of computational methods, illustrated with the following applications:
• A 2D model of the General Fusion hydraulically compressed FRC, using a radially compressing cylindrical coordinate system.
• A 2D model of the ELF thruster experiment with entrainment of neutrals.
• A 3D model of the ZaP flow-stabilized Z-pinch experiment, featuring multiple grid blocks to represent non-axisymmetric extrusions.
• A 3D model of the SSX spheromak experiment.