Direct numerical simulations of the $\mathsf{\kappa}$-mechanism

Gastine, T.; Dintrans, B.

doi:10.1051/0004-6361:20078936

Cited by 18 publications

(8 citation statements)

References 34 publications

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“…• Thermal instability and mixing (C.-C. Yang & Krumholz, 2012), • Implicit solver for temperature (Gastine & Dintrans, 2008), • Dust-gas dynamics with mutual drag interaction (C.-C. Yang & Johansen, 2016;), • Boundary conditions for the solar atmosphere and HDF5 format (Philippe-A. Bourdin, 2020).…”

Section: High-level Functionalitymentioning

confidence: 99%

The Pencil Code, a modular MPI code for partial differential equations and particles: multipurpose and multiuser-maintained

Brandenburg¹,

Johansen²,

Bourdin³

et al. 2021

JOSS

116

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Section: High-level Functionalitymentioning

confidence: 99%

The Pencil Code, a modular MPI code for partial differential equations and particles: multipurpose and multiuser-maintained

Brandenburg¹,

Johansen²,

Bourdin³

et al. 2021

JOSS

116

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“…In order to easily investigate the influence of the opacity bump on the stability, we adopt the following conductivity hollow to mimic this bump (as κ ∝ 1/K, see Gastine and Dintrans 2008a, hereafter Paper I):…”

Section: The First Step: Radiative Models In 1-dmentioning

confidence: 99%

Numerical simulations of the κ-mechanism with convection

Gastine¹,

Dintrans²

2010

Synergies Between Solar and Stellar Modelling

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A strong coupling between convection and pulsations is known to play a major role in the disappearance of unstable modes close to the red edge of the classical Cepheid instability strip. As mean-field models of time-dependent convection rely on weaklyconstrained parameters (e.g. Baker 1987), we tackle this problem by the means of 2-D Direct Numerical Simulations (DNS) of κ-mechanism with convection.Using a linear stability analysis, we first determine the physical conditions favourable to the κ-mechanism to occur inside a purely-radiative layer. Both the instability strips and the nonlinear saturation of unstable modes are then confirmed by the corresponding DNS. We next present the new simulations with convection, where a convective zone and the driving region overlap. The coupling between the convective motions and acoustic modes is then addressed by using projections onto an acoustic subspace.

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“…In Gastine & Dintrans (2008a) and Gastine & Dintrans (2008b) (hereafter Papers I and II), we have modelled the κmechanism in Cepheids by a simplified approach, that is, the propagation of acoustic waves in a layer of perfect gas in which the ionisation region is shaped by a hollow in the radiative conductivity profile. We recall that the instability of Cepheid variables relies on the blocking of the emerging radiative flux near the opacity bumps that are due to the ionisation of light elements like H or He.…”

Section: Introductionmentioning

confidence: 99%

Convective quenching of stellar pulsations

Gastine

Dintrans

2011

A&A

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Context. We study the convection-pulsation coupling that occurs in cold Cepheids close to the red edge of the classical instability strip. In these stars, the surface convective zone is supposed to stabilise the radial oscillations excited by the κ-mechanism. Aims. We study the influence of the convective motions on the amplitude and the nonlinear saturation of acoustic modes excited by κ-mechanism. We are interested in determining the physical conditions needed to lead to a quenching of oscillations by convection. Methods. We compute two-dimensional nonlinear simulations (DNS) of the convection-pulsation coupling, in which the oscillations are sustained by a continuous physical process: the κ-mechanism. Thanks to both a frequential analysis and a projection of the physical fields onto an acoustic subspace, we study how the convective motions affect the unstable radial oscillations. Results. Depending on the initial physical conditions, two main behaviours are obtained. (i) Either the unstable fundamental acoustic mode has a large amplitude, carries the bulk of the kinetic energy, and shows a nonlinear saturation similar to the purely radiative case; (ii) or the convective motions significantly affect the mode amplitude, which remains very weak. In this second case, convection is quenching the acoustic oscillations. We interpret these discrepancies in terms of the difference in density contrast: larger stratification leads to smaller convective plumes that do not affect the purely radial modes much, while large-scale vortices may quench the oscillations.

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Direct numerical simulations of the $\mathsf{\kappa}$-mechanism

Cited by 18 publications

References 34 publications

The Pencil Code, a modular MPI code for partial differential equations and particles: multipurpose and multiuser-maintained

The Pencil Code, a modular MPI code for partial differential equations and particles: multipurpose and multiuser-maintained

Numerical simulations of the κ-mechanism with convection

Convective quenching of stellar pulsations

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