Non-Boussinesq low-Prandtl number convection with a temperature-dependent thermal diffusivity

Abstract

In an attempt to understand the role of the strong radial dependence of thermal diffusivity on the properties of convection in sun-like stars, we mimic that effect in non-Oberbeck-Boussinesq (NOB) convection in a horizontally-extended rectangular domain (aspect ratio 16), by allowing the thermal diffusivity $\kappa$ to increase with the temperature (as in the case of stars). Direct numerical simulations (i.e., numerical solutions of the governing equations by resolving up to the smallest scales without requiring any modeling) show that, in comparison with Oberbeck-Boussinesq (OB) simulations (two of which we perform for comparison purposes), the symmetry of the temperature field about the mid-horizontal plane is broken, whereas the velocity and heat flux profiles remain essentially symmetric. Our choice of $\kappa (T)$, which resembles the variation in stars, results in the temperature field that loses its fine structures towards the hotter part of the computational domain, but the characteristic large scale of the turbulent thermal `superstructures', which are structures whose size is typically larger than the depth of the convection domain, continue to be largely independent of the depth.

arXiv comment17 pages, 13 figures

References in corpus (31)

• Large scale dynamics in turbulent Rayleigh-Benard convection
• The stellar atmosphere simulation code Bifrost
• Simulations of stellar convection with CO5BOLD
• The Stagger-grid: A Grid of 3D Stellar Atmosphere Models - I. Methods and General Properties
• Structure and Evolution of Giant Cells in Global Models of Solar Convection
• Turbulent superstructures in Rayleigh-Bénard convection
• Effects of compressibility on driving zonal flow in gas giants
• Aspect ratio dependence of heat transfer and large-scale flow in turbulent convection
• Turbulent thermal superstructures in Rayleigh-Bénard convection
• Phenomenology of buoyancy-driven turbulence: recent results
• Resolving the fine-scale structure in turbulent Rayleigh-Benard convection
• Seismic Sounding of Convection in the Sun
• Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
• On the role of tachoclines in solar and stellar dynamos
• Scaling of large-scale quantities in Rayleigh-Bénard convection
• Global and local statistics in turbulent convection at low Prandtl numbers
• Convective dynamos in spherical wedge geometry
• Stellar mixing length theory with entropy rain
• Large-scale mean patterns in turbulent convection
• Coherence of temperature and velocity superstructures in turbulent Rayleigh-Bénard flow
• Comparison of solar photospheric bright points between SUNRISE observations and MHD simulations
• Transitional boundary layers in low-Prandtl-number convection
• Supergranulation as the largest buoyantly driven convective scale of the Sun
• Probing turbulent superstructures in Rayleigh-Bénard convection by Lagrangian trajectory clusters
• Thermal boundary layer structure in low-Prandtl-number turbulent convection
• Mesoscale flows in large aspect ratio simulations of turbulent compressible convection
• Resolved energy budget of superstructures in Rayleigh-Bénard convection
• Convective velocity suppression via the enhancement of subadiabatic layer: Role of the effective Prandtl number
• Entropy Rain: Dilution and Compression of Thermals in Stratified Domains
• The magnitude of viscous dissipation in strongly stratified two-dimensional convection
• Effects of variable thermal diffusivity on the structure of convection

Cited by in corpus (11)

• Combined particle image velocimetry and thermometry of turbulent superstructures in thermal convection
• Convective mesoscale turbulence at very low Prandtl numbers
• Thermal boundary condition studies in large aspect ratio Rayleigh-Bénard convection
• Non-Boussinesq convection at low Prandtl numbers relevant to the Sun
• Similarities between characteristics of convective turbulence in confined and extended domains
• Effect of boundary conditions in turbulent thermal convection
• Strongly superadiabatic and stratified limits of compressible convection
• Turbulent mesoscale convection in the Boussinesq limit and beyond
• Large-scale circulations in a shear-free convective turbulence: Mean-field simulations
• Compressible turbulent convection: The role of temperature-dependent thermal conductivity and dynamic viscosity
• Molecular hints of two-step transition to convective flow via streamline percolation