The cellular burning regime in type Ia supernova explosions

Röpke, F. K.; Hillebrandt, W.; Niemeyer, J. C.

doi:10.1051/0004-6361:20035778

Cited by 32 publications

(19 citation statements)

References 34 publications

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“…Although the most satisfactory approach to the problem would be to reveal the mechanism from first physical principles, this is an exceedingly difficult task in view of the many different length and temporal scales involved and of the huge diversity of initial conditions that can be imagined. Even though some advances have been brought about (Khokhlov 1991;Khokhlov et al 1997;Niemeyer & Woosley 1997;Niemeyer 1999;Lisewski et al 2000;Röpke et al 2004;Zingale & Dursi 2007) no sound mechanism for the transition has yet been found. Given the lack of a consistent physical picture of the DDT mechanism the opposite path is usually taken, trying to constrain the conditions of DDT by comparing the resulting explosion with the observational data of SNIa.…”

Section: Discussionmentioning

confidence: 99%

A three-dimensional picture of the delayed-detonation model of type Ia supernovae

Bravo¹,

Garcı́a-Senz²

2007

A&A

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Aims. Deflagration models poorly explain the observed diversity of SNIa. Current multidimensional simulations of SNIa predict a significant amount of, so far unobserved, carbon and oxygen moving at low velocities. It has been proposed that these drawbacks can be resolved if there is a sudden jump to a detonation (delayed detonation), but these kinds of models have been explored mainly in one dimension. Here we present new three-dimensional delayed detonation models in which the deflagraton-to-detonation transition (DDT) takes place in conditions like those favored by one-dimensional models. Methods. We have used a smoothed-particle-hydrodynamics code adapted to follow all the dynamical phases of the explosion, with algorithms devised to handle subsonic as well as supersonic combustion fronts. The starting point was a centrally ignited C-O white dwarf of 1.38 M . When the average density on the flame surface reached ∼2−3 × 10 7 g cm −3 a detonation was launched. Results. The detonation wave processed more than 0.3 M of carbon and oxygen, emptying the central regions of the ejecta of unburned fuel and raising its kinetic energy close to the fiducial 10 51 erg expected from a healthy type Ia supernova. The final amount of 56 Ni synthesized also was in the correct range. However, the mass of carbon and oxygen ejected is still too high. Conclusions. The three-dimensional delayed detonation models explored here show an improvement over pure deflagration models, but they still fail to coincide with basic observational constraints. However, there are many aspects of the model that are still poorly known (geometry of flame ignition, mechanism of DDT, properties of detonation waves traversing a mixture of fuel and ashes). Therefore, it will be worth pursuing its exploration to see if a good SNIa model based on the three-dimensional delayed detonation scenario can be obtained.

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Section: Discussionmentioning

confidence: 99%

A three-dimensional picture of the delayed-detonation model of type Ia supernovae

Bravo¹,

Garcı́a-Senz²

2007

A&A

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“…Previous studies of flames interacting with turbulence have focused on flames interacting with vortical flow (see the twodimensional simulations presented in Röpke et al 2004) or statistical methods using one-dimensional turbulence ( Lisewski et al 2000a( Lisewski et al , 2000b). An open question is whether in the distributed burning regime a mixed region of partially burned fuel and ash can grow large enough that it can ignite a detonation ( Niemeyer & Woosley 1997;Khokhlov et al 1997;Niemeyer 1999).…”

Section: à3mentioning

confidence: 99%

Turbulence‐Flame Interactions in Type Ia Supernovae

Aspden

Bell

Day

et al. 2008

Astrophysical Journal

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The large range of time and length scales involved in Type Ia supernovae (SNe Ia) requires the use of flame models. As a prelude to exploring various options for flame models, we consider in this paper high-resolution, three-dimensional simulations of the small-scale dynamics of nuclear flames in the supernova environment in which the details of the flame structure are fully resolved. The range of densities examined, (1Y8) ; 10 7 g cm À3 , spans the transition from the laminar flamelet regime to the distributed burning regime where small-scale turbulence disrupts the flame. The use of a low Mach number algorithm facilitates the accurate resolution of the thermal structure of the flame and the inviscid turbulent kinetic energy cascade, while implicitly incorporating kinetic energy dissipation at the grid-scale cutoff. For an assumed background of isotropic Kolmogorov turbulence with an energy characteristic of SNe Ia, we find a transition density between 1 and 3 ; 10 7 g cm À3 , where the nature of the burning changes qualitatively. By 1 ; 10 7 g cm À3 , energy diffusion by conduction and radiation is exceeded, on the flame scale, by turbulent advection. As a result, the effective Lewis number approaches unity. That is, the flame resembles a laminar flame but is turbulently broadened with an effective diffusion coefficient, D T $ u 0 l, where u 0 is the turbulent intensity and l is the integral scale. For the larger integral scales characteristic of a real supernova, the flame structure is predicted to become complex and unsteady. Implications for a possible transition to detonation are discussed.

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“…For example, Im et al mention a quadratic dependence on the turbulence velocity in the case of weak turbulence [34]. On the other hand, Röpke et al report a linear relation even for turbulence velocities which are only marginally larger than the laminar flame speed in two-dimensional numerical simulations [35]. However, this result is possibly unsubstantial for the three-dimensional case.…”

Section: The Turbulent Flame Speed Relationmentioning

confidence: 99%

“…Hence, the corresponding spatial averages in equation (35) will not be sufficiently well behaved at the beginning. Although, the dynamics is dominated by the fuel domain at this point, both the enumerator and dominator in equation (35) are smoothed in time via convolution with an exponential damping function in order to remove strong oscillations in the ash and flame regions. The characteristic time scale of smoothing is prescribed by the parameter T .…”

Section: The Semi-localized Modelmentioning

confidence: 99%

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

Schmidt

Hillebrandt

Niemeyer

2005

Combustion Theory and Modelling

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We study the dynamics of thermonuclear flames propagating in fuel stirred by stochastic forcing. The fuel consists of carbon and oxygen in a state which is encountered in white dwarfs close to the Chandrasekhar limit. The level set method is applied to represent the flame fronts numerically. The computational domain for the numerical simulations is cubic, and periodic boundary conditions are imposed. The goal is the development of a suitable flame speed model for the small-scale dynamics of turbulent deflagration in thermonuclear supernovae. Because the burning process in a supernova explosion is transient and spatially inhomogeneous, the localized determination of subgrid scale closure parameters is essential. We formulate a semi-localized model based on the dynamical equation for the subgrid scale turbulence energy k sgs . The turbulent flame speed s t is of the order 2k sgs . In particular, the subgrid scale model features a dynamic procedure for the calculation of the turbulent energy transfer from resolved toward subgrid scales, which has been successfully applied to combustion problems in engineering. The options of either including or suppressing inverse energy transfer in the turbulence production term are compared. In combination with the piece-wise parabolic method for the hydrodynamics, our results favour the latter option. Moreover, different choices for the constant of proportionality in the asymptotic flame speed relation, s t ∝ 2k sgs , are investigated.

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The cellular burning regime in type Ia supernova explosions

Cited by 32 publications

References 34 publications

A three-dimensional picture of the delayed-detonation model of type Ia supernovae

A three-dimensional picture of the delayed-detonation model of type Ia supernovae

Turbulence‐Flame Interactions in Type Ia Supernovae

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

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