Coupled magnetogasdynamics: Radiative transfer computing using unstructured meshes

Coupled magnetogasdynamics: Radiative transfer computing using unstructured meshes

Boldarev, A..
Chetverushkin, B.N.
Kartasheva, E.L.
Gasilov, V.A.
D'yachenko, S.V.
Olkhovskaya, O.G.

2006-09-05

We present a new object-oriented radiative-magnetogasdynamics (RMHD) code based on unstructured grid technology which is expected to be a convenient tool for investigations of plasma dynamics in various pulsed-power facilities. High-performance computing is a proper tool for simulations of complex multiscale nonlinear processes like transient flows of strongly radiative multicharged plasmas. The first tests of this new code have showed promising results. The code performs calculations in (r-z) and (x-y) coordinates. We accept a single-fluid MHD model [1]. The MHD-equations are written in a 2.5D approximation, i.e. the main flowfield vectors are presented by all three components. Anisotropy of dissipative processes in the presence of magnetic field is accounted. The electron-ion energy relaxation is included. Radiative energy transfer is described by the equation for spectral radiation intensity. To overcome the inhomogeneity of magnetically-driven plasmas we solve the radiative transport equation by means of semi-analytical characteristic algorithm. An additional grid of rays is necessary for its implementation. A modified FE-DSN-method [2] as well as the method based on the adjoint radiative transfer problem solution [3] are also developed and put into practice. The radiative energy transfer is calculated via multigroup spectral approximation. For practical applications the datatables of plasma properties as to thermodynamics, ionisation state, opacities and emissivities are used. The MHD equations written as conservation laws are discretized by means of a finite-volume method. The set of finite volumes is built for basic unstructured triangular mesh. All the physical variables are located in the triangular grid nodes. A splitting scheme is applied to the full MHD system. The procedure of time-advance is an explicit second-order predictor-corrector. A general monotonous reconstruction of mesh-defined functions was designed with respect to the dependence on two variables and a generalized quasi-monotonous Lax-Friedrichs-Tadmor scheme was developed [4]. The explicit difference scheme allows quite natural parallel implementation for distributed computer systems. A technique of margins was suggested for data exchange between subdomains with unstructured grids located at different processors. The designed code was applied to simulations of a dense strongly radiative Z-pinches formed of an exploded multiwire array. Comparisons with experimental data obtained in Sandia National Laboratory (USA) are presented.

MHD
radiative transfer
unstructured mesh

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Conference proceedings

conference paper

(c) 2006 Boldarev, A..; Chetverushkin, B.N.; Kartasheva, E.L.; Gasilov, V.A.; D'yachenko, S.V.; Olkhovskaya, O.G.