Abstract
A plasma transport model has been implemented in an Eulerian AMR radiation-hydrodynamics code, xRage, which includes plasma viscosity in the momentum tensor, viscous dissipation in the energy equations, and binary species mixing with consistent species mass and energy fluxes driven by concentration gradients, ion and electron baro-diffusion terms and temperature gradient forces. The physics basis, computational issues, numeric options, and results from several test problems are discussed. The transport coefficients are found to be relatively insensitive to the kinetic correction factors when the concentrations are expressed with the molar fractions and the ion mass differences are large. The contributions to flow dynamics from plasma viscosity and mass diffusion were found to increase significantly as scale lengths decrease in an inertial confinement fusion relevant Kelvin-Helmholtz instability mix layer. The mixing scale lengths in the test case are on the order of 100 μm and smaller for viscous effects to appear and 10 μm or less for significant ion species diffusion, evident over durations on the order of nanoseconds. The temperature gradient driven mass flux is seen to deplete a high Z tracer ion at the ion shock front. The plasma transport model provides the generation of the atomic mix per unit of interfacial area between two species with no free parameters. The evolution of the total atomic mix then depends also on an accurate resolution or estimate of the interfacial area between the species mixing by plasma transport. High resolution simulations or a more Lagrangian-like treatment of species interfaces may be required to distinguish plasma transport and numerical diffusion in an Eulerian computation of complex and dynamically evolving mix regions.
Highlights
Performance in ICF has been predicted largely by fluid-based CFD codes.1–5 A long standing explanation of poor performance of experiments relative to computed predictions is the mix of the fuel and imploding capsule materials
A plasma transport model has been implemented in an Eulerian AMR radiation-hydrodynamics code, xRage, which includes plasma viscosity in the momentum tensor, viscous dissipation in the energy equations, and binary species mixing with consistent species mass and energy fluxes driven by concentration gradients, ion and electron baro-diffusion terms and temperature gradient forces
042702-3 Vold et al The kinetic correction factor ak111⁄2v is expressed as a function of the molar fraction in the mixing layer and is equivalent to that derived in Ref. 20 evaluated as ak11 1⁄4 ak111⁄2DI1⁄2v
Summary
Performance in ICF (inertial confinement fusion) has been predicted largely by fluid-based CFD (computational fluid dynamics) codes. A long standing explanation of poor performance of experiments relative to computed predictions is the mix of the fuel and imploding capsule materials. ICF codes, for the most part, have not previously included self-consistent plasma transport as a possible mechanism degrading the performance some recent studies hint at plasma viscosity, viscous energy dissipation, and mass diffusivity as potentially important mechanisms.. ICF codes, for the most part, have not previously included self-consistent plasma transport as a possible mechanism degrading the performance some recent studies hint at plasma viscosity, viscous energy dissipation, and mass diffusivity as potentially important mechanisms.14–19 This motivated us to implement a plasma transport model into an Eulerian AMR (adaptive mesh refinement) fluid code, xRage.. As studies move to higher fidelity physics and greater resolution, it is anticipated that plasma transport will be important in predicting atomic mixing and viscous effects in. Numerical issues and implications for distinguishing transport from numerical mixing are summarized
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