Level set simulations of turbulent thermonuclear deflagration in degenerate carbon and oxygen

Schmidt, Wolfgang; Hillebrandt, W.; Niemeyer, J. C.

doi:10.1080/13647830500304854

Cited by 19 publications

(23 citation statements)

References 40 publications

(106 reference statements)

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“…On the other hand, C ν becomes smaller than 0.1 if the SGS turbulence velocity exceeds a few percent of the speed of sound. This behaviour of the eddy-viscosity parameter is qualitatively different from the prediction of the dynamical procedure which implies less energy transfer if turbulence is still developing but enhanced transfer in the fully developed case (Schmidt et al 2005). This is clearly reflected in the time evolution of the turbulence energy in two simulations which differ only in the SGS model.…”

Section: Numerical Simulationsmentioning

confidence: 70%

A localised subgrid scale model for fluid dynamical simulations in astrophysics

Schmidt

Niemeyer

Hillebrandt

et al. 2006

A&A

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120

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The dynamics of the explosive burning process is highly sensitive to the flame speed model in numerical simulations of type Ia supernovae. Based upon the hypothesis that the effective flame speed is determined by the unresolved turbulent velocity fluctuations, we employ a new subgrid scale model which includes a localised treatment of the energy transfer through the turbulence cascade in combination with semistatistical closures for the dissipation and non-local transport of turbulence energy. In addition, subgrid scale buoyancy effects are included. In the limit of negligible energy transfer and transport, the dynamical model reduces to the Sharp-Wheeler relation. According to our findings, the Sharp-Wheeler relation is insuffcient to account for the complicated turbulent dynamics of flames in thermonuclear supernovae. The application of a co-moving grid technique enables us to achieve very high spatial resolution in the burning region. Turbulence is produced mostly at the flame surface and in the interior ash regions. Consequently, there is a pronounced anisotropy in the vicinity of the flame fronts. The localised subgrid scale model predicts significantly enhanced energy generation and less unburnt carbon and oxygen at low velocities compared to earlier simulations.

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Section: Numerical Simulationsmentioning

confidence: 70%

A localised subgrid scale model for fluid dynamical simulations in astrophysics

Schmidt

Niemeyer

Hillebrandt

et al. 2006

A&A

Self Cite

120

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“…As is discussed at length in Schmidt et al (2005), the discrepancy can be attributed to a difficulty related to inverse energy transfer. Since backscattering injects energy on the smallest resolved scales, which are sizeably affected by numerical dissipation, the kinetic energy added to the flow is more or less instantaneously converted into internal energy.…”

Section: Turbulent Burning In a Boxmentioning

confidence: 99%

“…L can be interpreted as integral length scale of the flow. An detailed description of the methodology and a discussion of numerous simulations is given in Schmidt et al (2005).…”

Section: Turbulent Burning In a Boxmentioning

confidence: 99%

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A localised subgrid scale model for fluid dynamical simulations in astrophysics

Schmidt

Niemeyer²,

Hillebrandt

2006

A&A

Self Cite

120

149

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We present a one-equation subgrid scale model that evolves the turbulence energy corresponding to unresolved velocity fluctuations in large eddy simulations. The model is derived in the context of the Germano consistent decomposition of the hydrodynamical equations. The eddyviscosity closure for the rate of energy transfer from resolved toward subgrid scales is localised by means of a dynamical procedure for the computation of the closure parameter. Therefore, the subgrid scale model applies to arbitrary flow geometry and evolution. For the treatment of microscopic viscous dissipation a semi-statistical approach is used, and the gradient-diffusion hypothesis is adopted for turbulent transport. A priori tests of the localised eddy-viscosity closure and the gradient-diffusion closure are made by analysing data from direct numerical simulations. As an a posteriori testing case, the large eddy simulation of thermonuclear combustion in forced isotropic turbulence is discussed. We intend the formulation of the subgrid scale model in this paper as a basis for more advanced applications in numerical simulations of complex astrophysical phenomena involving turbulence.

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“…Other studies concerned the validity of subgrid-scale models of the interaction of the flame with turbulence (Schmidt et al, 2005a). This interaction was also simulated by Niemeyer et al (1999).…”

Section: Complementary Small-scale Simulationsmentioning

confidence: 99%