Niemeyer, J

[["dc.bibliographiccitation.firstpage","1683"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","The Astrophysical Journal"],["dc.bibliographiccitation.lastpage","1693"],["dc.bibliographiccitation.volume","710"],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Ciaraldi-Schoolmann, F."],["dc.contributor.author","Niemeyer, J. C."],["dc.contributor.author","Roepke, F. K."],["dc.contributor.author","Hillebrandt, W."],["dc.date.accessioned","2018-11-07T08:45:52Z"],["dc.date.accessioned","2020-07-02T14:45:12Z"],["dc.date.available","2018-11-07T08:45:52Z"],["dc.date.available","2020-07-02T14:45:12Z"],["dc.date.issued","2010"],["dc.description.abstract","The delayed detonation model describes the observational properties of the majority of Type Ia supernovae very well. Using numerical data from a three-dimensional deflagration model for Type Ia supernovae, the intermittency of the turbulent velocity field and its implications on the probability of a deflagration-to-detonation (DDT) transition are investigated. From structure functions of the turbulent velocity fluctuations, we determine intermittency parameters based on the log-normal and the log-Poisson models. The bulk of turbulence in the ash regions appears to be less intermittent than predicted by the standard log-normal model and the She-Leveque model. On the other hand, the analysis of the turbulent velocity fluctuations in the vicinity of the flame front by Ropke suggests a much higher probability of large velocity fluctuations on the grid scale in comparison to the log-normal intermittency model. Following Pan et al., we computed probability density functions for a DDT for the different distributions. The determination of the total number of regions at the flame surface, in which DDTs can be triggered, enables us to estimate the total number of events. Assuming that a DDT can occur in the stirred flame regime, as proposed by Woosley et al., the log-normal model would imply a delayed detonation between 0.7 and 0.8 s after the beginning of the deflagration phase for the multi-spot ignition scenario used in the simulation. However, the probability drops to virtually zero if a DDT is further constrained by the requirement that the turbulent velocity fluctuations reach about 500 km s(-1). Under this condition, delayed detonations are only possible if the distribution of the velocity fluctuations is not log-normal. From our calculations follows that the distribution obtained by Ropke allow for multiple DDTs around 0.8 s after ignition at a transition density close to 1 x 107 g cm(-3)."],["dc.identifier.doi","10.1088/0004-637X/710/2/1683"],["dc.identifier.isi","000274233300061"],["dc.identifier.scopus","2-s2.0-77149168162"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/20548"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-77149168162&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.eissn","1538-4357"],["dc.relation.issn","0004-637X"],["dc.title","Turbulence in a three-dimensional deflagration model for type Ia Supernovae. II. Intermittency and the deflagration-to-detonation transition probability"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","952"],["dc.bibliographiccitation.issue","2 I"],["dc.bibliographiccitation.journal","The Astrophysical Journal"],["dc.bibliographiccitation.lastpage","961"],["dc.bibliographiccitation.volume","588"],["dc.contributor.author","Röpke, F. K."],["dc.contributor.author","Niemeyer, J. C."],["dc.contributor.author","Hillebrandt, W."],["dc.date.accessioned","2020-07-21T06:08:10Z"],["dc.date.available","2020-07-21T06:08:10Z"],["dc.date.issued","2003"],["dc.description.abstract","We present a numerical model which allows us to investigate thermonuclear flames in Type Ia supernova explosions. The model is based on a finite-volume explicit hydrodynamics solver employing PPM. Using the level-set technique combined with in-cell reconstruction and flux-splitting schemes we are able to describe the flame in the discontinuity approximation. We apply our implementation to flame propagation in Chandrasekhar-mass Type Ia supernova models. In particular we concentrate on intermediate scales between the flame width and the Gibson-scale, where the burning front is subject to the Landau-Darrieus instability. We are able to reproduce the theoretical prediction on the growth rates of perturbations in the linear regime and observe the stabilization of the flame in a cellular shape. The increase of the mean burning velocity due to the enlarged flame surface is measured. Results of our simulation are in agreement with semianalytical studies."],["dc.identifier.doi","10.1086/374216"],["dc.identifier.scopus","2-s2.0-0041760782"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/67316"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-0041760782&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.relation.eissn","1538-4357"],["dc.relation.issn","0004-637X"],["dc.title","On the small-scale stability of thermonuclear flames in type ia supernovae"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","14"],["dc.bibliographiccitation.volume","448"],["dc.contributor.author","Röpke, F. K."],["dc.contributor.author","Hillebrandt, W."],["dc.contributor.author","Niemeyer, J. C."],["dc.contributor.author","Woosley, S. E."],["dc.date.accessioned","2020-07-09T08:36:38Z"],["dc.date.available","2020-07-09T08:36:38Z"],["dc.date.issued","2006"],["dc.description.abstract","We present a systematic survey of the capabilities of type Ia supernova explosion models starting from a number of flame seeds distributed around the center of the white dwarf star. To this end we greatly improved the resolution of the numerical simulations in the initial stages. This novel numerical approach facilitates a detailed study of multi-spot ignition scenarios with up to hundreds of ignition sparks. Two-dimensional simulations are shown to be inappropriate to study the effects of initial flame configurations. Based on a set of three-dimensional models, we conclude that multi-spot ignition scenarios may improve type Ia supernova models towards better agreement with observations. The achievable effect reaches a maximum at a limited number of flame ignition kernels as shown by the numerical models and corroborated by a simple dimensional analysis."],["dc.identifier.doi","10.1051/0004-6361:20053926"],["dc.identifier.scopus","2-s2.0-33644906974"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/66905"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-33644906974&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","Multi-spot ignition in type la supernova models"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","386"],["dc.contributor.author","Reinecke, M."],["dc.contributor.author","Hillebrandt, W."],["dc.contributor.author","Niemeyer, J. C."],["dc.date.accessioned","2020-07-03T07:18:17Z"],["dc.date.available","2020-07-03T07:18:17Z"],["dc.date.issued","2002"],["dc.identifier.scopus","2-s2.0-0036570811"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/66852"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-0036570811&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.title","Refined numerical models for multidimensional type Ia supernova simulations"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","411"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","422"],["dc.bibliographiccitation.volume","420"],["dc.contributor.author","Röpke, F. K."],["dc.contributor.author","Hillebrandt, W."],["dc.contributor.author","Niemeyer, J. C."],["dc.date.accessioned","2020-07-07T13:31:54Z"],["dc.date.available","2020-07-07T13:31:54Z"],["dc.date.issued","2004"],["dc.description.abstract","We present a numerical investigation of the cellular burning regime in Type Ia supernova explosions. This regime holds at small scales (i.e. below the Gibson scale), which are unresolved in large-scale Type Ia supernova simulations. The fundamental effects that dominate the flame evolution here are the Landau-Darrieus instability and its nonlinear stabilization, leading to a stabilization of the flame in a cellular shape. The flame propagation into quiescent fuel is investigated addressing the dependence of the simulation results on the specific parameters of the numerical setup. Furthermore, we investigate the flame stability at a range of fuel densities. This is directly connected to the questions of active turbulent combustion (a mechanism of flame destabilization and subsequent self-turbulization) and a deflagration-to-detonation transition of the flame. In our simulations we find no substantial destabilization of the flame when propagating into quiescent fuels of densities down to ~10^7 g/cm^3, corroborating fundamental assumptions of large-scale SN Ia explosion models. For these models, however, we suggest an increased lower cutoff for the flame propagation velocity to take the cellular burning regime into account."],["dc.identifier.doi","10.1051/0004-6361:20035721"],["dc.identifier.scopus","2-s2.0-2942524063"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/66884"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-2942524063&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","The cellular burning regime in type ia supernova explosions I. Flame propagation into quiescent fuel"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","337"],["dc.bibliographiccitation.lastpage","348"],["dc.contributor.author","Hillebrandt, W."],["dc.contributor.author","Niemeyer, J. C."],["dc.date.accessioned","2020-07-16T13:15:36Z"],["dc.date.available","2020-07-16T13:15:36Z"],["dc.date.issued","1997"],["dc.description.abstract","We argue that a reliable model of thermonuclear burning in the degenerate matter of a C+O white dwarf must include a method to deal with the physics of turbulent combustion. Guided by an analysis of instabilities on various length scales we present such a model, which may help to overcome problems of recent attempts to explain type Ia supernova outbursts my means of thermonuclear deflagration fronts."],["dc.identifier.doi","10.1007/978-94-011-5710-0_22"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/67198"],["dc.language.iso","en"],["dc.publisher","Springer Nature"],["dc.relation.eisbn","978-94-011-5710-0"],["dc.relation.isbn","978-94-010-6408-8"],["dc.relation.ispartof","Thermonuclear Supernovae"],["dc.title","Turbulence and Thermonuclear Burning"],["dc.type","book_chapter"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.volume","11"],["dc.contributor.author","Hillebrandt, W."],["dc.contributor.author","Reinecke, M."],["dc.contributor.author","Röpke, F. K."],["dc.contributor.author","Stehle, M."],["dc.contributor.author","Travaglio, C."],["dc.contributor.author","Niemeyer, J. C."],["dc.contributor.editor","Jorissen, A."],["dc.contributor.editor","Goriely, S."],["dc.contributor.editor","Rayet, M."],["dc.contributor.editor","Siess, L."],["dc.contributor.editor","Boffin, H."],["dc.date.accessioned","2020-07-16T13:04:44Z"],["dc.date.available","2020-07-16T13:04:44Z"],["dc.date.issued","2004"],["dc.description.abstract","Recent progress in modeling type Ia supernovae by means of 3-dimensional hydrodynamic simulations as well as several of the still open questions are addressed. Our models are based on the assumption that thermonuclear burning inside a Chandrasekhar-mass C+O white dwarf is similar to turbulent chemical combustion and that, thus, thermonuclear supernovae can be modeled by means of numerical methods which have been developed and tested for laboratory and technical flames. It is shown that the new models have considerable predictive power and allow to study observable properties of type Ia supernovae, such as their light curves and spectra, without adjustable non-physical parameters, and they make firm predictions for the nucleosynthesis yields from the explosions. This raises a quest for better data, covering the spectroscopical and photometric evolution in all wave bands from very early epochs all the way into the nebular phase. First such results obtained by the European Supernova Collaboration (ESC) for a sample of nearby SNe Ia and their implications for constraining the models and systematic differences between them are also discussed."],["dc.identifier.doi","10.1051/eas:2004010"],["dc.identifier.scopus","2-s2.0-28844472915"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/67196"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-28844472915&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.publisher","EDP Sciences"],["dc.relation.crisseries","EAS Publications Series"],["dc.relation.ispartofseries","EAS Publications Series;"],["dc.title","Thermonuclear supernovae"],["dc.type","book"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","229"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Nuclear Physics. A, Nuclear and Hadronic Physics"],["dc.bibliographiccitation.lastpage","238"],["dc.bibliographiccitation.volume","723"],["dc.contributor.author","Hillebrandt, W."],["dc.contributor.author","Niemeyer, J. C."],["dc.contributor.author","Reinecke, M."],["dc.contributor.author","Röpke, F."],["dc.contributor.author","Travaglio, C."],["dc.date.accessioned","2020-07-22T09:29:46Z"],["dc.date.available","2020-07-22T09:29:46Z"],["dc.date.issued","2003"],["dc.description.abstract","Because calibrated light curves of type Ia supernovae have become a major tool to determine the local expansion rate of the Universe, considerable attention has been given to models of these events over the past couple of years. It is now common believe that perhaps most type Ia supernovae are the explosions of white dwarfs that have approached the Chandrasekhar mass, MChan, ≈ 1.39 M⊙, and are disrupted by thermonuclear fusion of carbon and oxygen. However, the mechanism whereby such accreting carbon-oxygen white dwarfs explode continues to be uncertain. Recent progress in modeling type Ia supernovae as well as several of the still open questions are addressed in this article. Although the main emphasis will be on studies of the explosion mechanism itself and on the related physical processes, including the physics and nuclear physics of turbulent nuclear combustion in degenerate stars, observational implications and constraints will also be discussed."],["dc.identifier.doi","10.1016/S0375-9474(03)00719-X"],["dc.identifier.scopus","2-s2.0-0038181127"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/67381"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-0038181127&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.relation.issn","0375-9474"],["dc.title","Multidimensional simulations of type Ia supernova explosions and nucleosynthesis"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","265"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.lastpage","281"],["dc.bibliographiccitation.volume","450"],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Niemeyer, J. C."],["dc.contributor.author","Hillebrandt, W."],["dc.date.accessioned","2020-07-22T09:41:38Z"],["dc.date.available","2020-07-22T09:41:38Z"],["dc.date.issued","2006"],["dc.description.abstract","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 eddy-viscosity 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."],["dc.identifier.doi","10.1051/0004-6361:20053617"],["dc.identifier.scopus","2-s2.0-33645821906"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/67391"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-33645821906&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","A localised subgrid scale model for fluid dynamical simulations in astrophysics I. Theory and numerical tests"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","363"],["dc.bibliographiccitation.lastpage","384"],["dc.contributor.author","Hillebrandt, W."],["dc.contributor.author","Reinecke, M."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Röpke, F. K."],["dc.contributor.author","Travaglio, C."],["dc.contributor.author","Niemeyer, J. C."],["dc.contributor.editor","Warnecke, G."],["dc.date.accessioned","2020-07-09T08:04:23Z"],["dc.date.available","2020-07-09T08:04:23Z"],["dc.date.issued","2005"],["dc.description.abstract","Type Ia supernovae, i.e. stellar explosions which do not have hydrogen in their spectra, but intermediate-mass elements such as silicon, calcium, cobalt, and iron, have recently received considerable attention because it appears that they can be used as ”standard candles” to measure cosmic distances out to billions of light years away from us. Observations of type Ia supernovae seem to indicate that we are living in a universe that started to accelerate its expansion when it was about half its present age. These conclusions rest primarily on phenomenological models which, however, lack proper theoretical understanding, mainly because the explosion process, initiated by thermonuclear fusion of carbon and oxygen into heavier elements, is difficult to simulate even on supercomputers. Here, we investigate a new way of modeling turbulent thermonuclear deflagration fronts in white dwarfs undergoing a type Ia supernova explosion. Our approach is based on a level set method which treats the front as a mathematical discontinuity and allows for full coupling between the front geometry and the flow field. New results of the method applied to the problem of type Ia supernovae are obtained. It is shown that in 2-D with high spatial resolution and a physically motivated subgrid scale model for the nuclear flames numerically “converged” results can be obtained, but for most initial conditions the stars do not explode. In contrast, simulations in 3-D do give the desired explosions and many of their properties, such as the explosion energies, lightcurves and nucleosynthesis products, are in very good agreement with observed type Ia supernovae."],["dc.identifier.doi","10.1007/3-540-27907-5_16"],["dc.identifier.scopus","2-s2.0-35348925773"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/66897"],["dc.identifier.url","http://www.scopus.com/inward/record.url?eid=2-s2.0-35348925773&partnerID=MN8TOARS"],["dc.language.iso","en"],["dc.publisher","Springer"],["dc.publisher.place","Berlin, Heidelberg"],["dc.relation.doi","10.1007/3-540-27907-5"],["dc.relation.eisbn","978-3-540-27907-5"],["dc.relation.isbn","978-3-540-24834-7"],["dc.relation.ispartof","Analysis and Numerics for Conservation Laws"],["dc.title","Simulations of turbulent thermonuclear burning in type Ia supernovae"],["dc.type","book_chapter"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]