Emissivity of discretized diffusion problems

Densmore, Jeffery D.; Davidson, Gregory G.; Carrington, David B.

doi:10.1016/j.anucene.2006.02.006

Cited by 6 publications

(6 citation statements)

References 11 publications

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“…Densmore et al (2006) performs an emissivity based derivation to generalize the standard IMC-DDMC boundary condition and improve the emission from DDMC to IMC at spatial interfaces. If increased grid resolution in SuperNu increases the luminosity, then the alternate boundary condition presented by Densmore et al (2006) may increase the absolute bolometric magnitude of the light curve at the current 64 cell resolution. We have performed preliminary tests with an emissivity based boundary condition and find a ∼2% increase in the absolute bolometric magnitude at peak; despite this modest change, exploring the effects of increasing the spatial resolution may be revealing.…”

Section: W7 Testsmentioning

confidence: 99%

“…In particular, the standard leakage opacity at IMC-DDMC spatial method interfaces may underpredict particle transmission across cell surfaces when DDMC interface cells are optically thick (Densmore et al 2007). Densmore et al (2006) performs an emissivity based derivation to generalize the standard IMC-DDMC boundary condition and improve the emission from DDMC to IMC at spatial interfaces. If increased grid resolution in SuperNu increases the luminosity, then the alternate boundary condition presented by Densmore et al (2006) may increase the absolute bolometric magnitude of the light curve at the current 64 cell resolution.…”

Section: W7 Testsmentioning

confidence: 99%

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Radiation Transport for Explosive Outflows: Opacity Regrouping

Wollaeger¹,

Rossum²

2014

ApJS

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Implicit Monte Carlo (IMC) and Discrete Diffusion Monte Carlo (DDMC) are methods used to stochastically solve the radiative transport and diffusion equations, respectively. These methods combine into a hybrid transport-diffusion method we refer to as IMC-DDMC. We explore a multigroup IMC-DDMC scheme that, in DDMC, combines frequency groups with sufficient optical thickness. We term this procedure "opacity regrouping". Opacity regrouping has previously been applied to IMC-DDMC calculations for problems in which the dependence of the opacity on frequency is monotonic. We generalize opacity regrouping to non-contiguous groups and implement this in SuperNu, a code designed to do radiation transport in high-velocity outflows with non-monotonic opacities. We find that regrouping of non-contiguous opacity groups generally improves the speed of IMC-DDMC radiation transport. We present an asymptotic analysis that informs the nature of the Doppler shift in DDMC groups and summarize the derivation of the Gentile-Fleck factor for modified IMC-DDMC. We test SuperNu using numerical experiments including a quasi-manufactured analytic solution, a simple ten-group problem, and the W7 problem for Type Ia supernovae. We find that the opacity regrouping is necessary to make our IMC-DDMC implementation feasible for the W7 problem and possibly Type Ia supernova simulations in general. We compare the bolometric light curves and spectra produced by the SuperNu and PHOENIX radiation transport codes for the W7 problem. The overall shape of the bolometric light curves are in good agreement, as are the spectra and their evolution with time. However, for the numerical specifications we considered, we find that the peak luminosity of the light curve calculated using SuperNu is ∼10% less than that calculated using PHOENIX.

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Section: W7 Testsmentioning

confidence: 99%

Section: W7 Testsmentioning

confidence: 99%

Radiation Transport for Explosive Outflows: Opacity Regrouping

Wollaeger¹,

Rossum²

2014

ApJS

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“…Interface conditions can also be seamlessly integrated during a simulation allowing Monte Carlo particles to move between IMC and IMD regions. Densmore et al [9] have developed a rigorous interface condition that will preserve the analytic emissivity of a face that separates DDMC and IMC regions. We will apply this interface condition for the IMD-IMC interface in HIMCD.…”

Section: Hybrid Implicit Monte Carlo Diffusionmentioning

confidence: 99%

Using hybrid implicit Monte Carlo diffusion to simulate gray radiation hydrodynamics

Cleveland

Gentile

2015

Journal of Computational Physics

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This work describes how to couple a hybrid Implicit Monte Carlo Diffusion (HIMCD) method with a Lagrangian hydrodynamics code to evaluate the coupled radiation hydrodynamics equations. This HIMCD method dynamically applies Implicit Monte Carlo Diffusion (IMD) [1] to regions of a problem that are opaque and diffusive while applying standard Implicit Monte Carlo (IMC) [2] to regions where the diffusion approximation is invalid. We show that this method significantly improves the computational efficiency as compared to a standard IMC/Hydrodynamics solver, when optically thick diffusive material is present, while maintaining accuracy. Two test cases are used to demonstrate the accuracy and performance of HIMCD as compared to IMC and IMD. The first is the Lowrie semi-analytic diffusive shock [3]. The second is a simple test case where the source radiation streams through optically thin material and heats a thick diffusive region of material causing it to rapidly expand. We found that HIMCD proves to be accurate, robust, and computationally efficient for these test problems.

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“…We employ the diffusion transport interface condition originally developed by Densmore et al (2006) for an interface between IMC and DDMC. This in terface condition is defined such that it will preserve an accurate emissivity at the interface regardless of zone size (Densmore, 2006).…”

Section: The Diffusion-transport Spatial Interface Conditionmentioning

confidence: 99%