Developing and Benchmarking MH4D, A Tetrahedral Mesh MHD Code

Periodic boundary conditions, applicable to parallel and non-parallel planes have been developed. Mode selection is achieved by modeling a “slice” of a domain. For instance, modeling a 1/4-slice of a cylindrical Z-pinch geometry eliminates the m = 1,2, and 3 modes. M = 4 and higher modes will still be simulated. An insulating boundary condition has been developed. External circuits can be modeled by specifying electric and magnetic surface fields. A specified magnetic field simulates a circuit with constant current where Ampere’s law dictates the current flow. A specified electric field simulates a constant applied voltage. A constant current model is applicable to experiments with relatively high-impedance power supplies. To function with the insulating boundary condition, implicit and semi-implicit solvers require inclusion of surface terms. These solvers are being modified. Also, ionization physics capability is being developed. Progress in boundary condition development is presented, and a benchmarking and verification strategy is described.