Small-Peclet-number approximation for stellar turbulent mixing zones

Area of Science:

• Astrophysics
• Fluid Dynamics
• Plasma Physics

Background:

• Stellar interiors feature hydroradiative turbulent mixing zones.
• Radiative conductivity often dominates turbulent transport in these zones.

Purpose of the Study:

• Derive a small turbulent Péclet-small turbulent Mach number approximation for hydroradiative turbulent mixing zones.
• Extend existing Reynolds stress models to the small-Péclet regime.

Main Methods:

• Asymptotic analysis to determine orders of magnitude for fluctuating temperature, pressure, conduction, and velocity divergence.
• Development of a Reynolds stress model incorporating derived expressions.
• Three-dimensional direct numerical simulations of radiative Rayleigh-Taylor turbulent mixing zones.

Main Results:

• Validated asymptotic predictions for fluctuating quantities.
• Successfully extended Reynolds stress model to the small-Péclet regime.
• Confirmed the utility of the new model in simulating stellar interior phenomena.

Conclusions:

• The derived approximation accurately captures key physics in hydroradiative turbulent mixing zones.
• The enhanced Reynolds stress model provides a robust tool for astrophysical simulations.
• This work advances our understanding of turbulent transport in stellar environments.