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Planetary and stellar convection, which are compressible and turbulent, remain poorly understood. In this paper, we report numerical results on the scaling of Nusselt number ($\mathrm{Nu}$) and Reynolds number ($\mathrm{Re}$) for extreme…

Fluid Dynamics · Physics 2025-02-06 Harshit Tiwari , Mahendra K. Verma

(Abridged) We describe the results of three-dimensional (3D) numerical simulations designed to study turbulent convection in the stellar interiors, and compare them to stellar mixing-length theory (MLT). Simulations in 2D are significantly…

Astrophysics · Physics 2011-02-11 Casey A. Meakin , David Arnett

We study penetrative convection of a fluid confined between two horizontal plates, the temperatures of which are such that a temperature of maximum density lies between them. The range of Rayleigh numbers studied is $Ra = \left[10^6, 10^8…

Fluid Dynamics · Physics 2019-09-10 Srikanth Toppaladoddi , J. S. Wettlaufer

In this paper we estimate the relative strengths of various terms of the Rayleigh-B\'enard equations. Based on these estimates and scaling analysis, we derive a general formula for the large-scale velocity, $U$, or the P\'eclet number that…

Fluid Dynamics · Physics 2016-11-29 Ambrish Pandey , Abhishek Kumar , Anando G. Chatterjee , Mahendra K. Verma

Starting from hydrodynamic equations, we have established a set of hydrodynamic equations for average flow and a set of dynamic equations of auto- and cross-correlations of turbulent velocity and temperature fluctuations, following the…

Solar and Stellar Astrophysics · Physics 2018-08-30 D. R. Xiong , L. Deng , C. Zhang

The previous investigation on Rayleigh-B\'enard convection of a dilute classical gas [T. Kita: J. Phys. Soc. Jpn. {\bf 75} (2006) 124005] is extended to calculate entropy change of the convective transition with the rigid boundaries. We…

Statistical Mechanics · Physics 2009-11-13 Takafumi Kita

In the rapidly rotating limit, we derive a balanced set of reduced equations governing the strongly nonlinear development of the convective wall-mode instability in the interior of a general container. The model illustrates that wall-mode…

Many natural and industrial turbulent flows are subjected to time-dependent boundary conditions. Despite being ubiquitous, the influence of temporal modulations (with frequency $f$) on global transport properties has hardly been studied.…

Fluid Dynamics · Physics 2020-10-14 Rui Yang , Kai Leong Chong , Qi Wang , Roberto Verzicco , Olga Shishkina , Detlef Lohse

Quantifying transport by strongly stratified turbulence in low Prandtl number ($Pr$) fluids is critically important for the development of better models for the structure and evolution of stellar and planetary interiors. Motivated by recent…

Fluid Dynamics · Physics 2024-07-19 Kasturi Shah , Gregory P. Chini , Colm-cille P. Caulfield , Pascale Garaud

Using direct numerical simulations of turbulent thermal convection for Rayleigh number ($\mathrm{Ra}$) between $10^6$ and $10^8$ and unit Prandtl number, we derive scaling relations for viscous dissipation in the bulk and in the boundary…

Fluid Dynamics · Physics 2018-04-09 Shashwat Bhattacharya , Ambrish Pandey , Abhishek Kumar , Mahendra K. Verma

Direct measurements of the velocity in turbulent convection of $SF_6$ near its gas-liquid critical point by light scattering on the critical density fluctuations were conducted. The temperature, velocity and cross frequency power spectra in…

chao-dyn · Physics 2009-10-31 Shay Ashkenazi , Victor Steinberg

In this paper, we calibrate the coefficients for the one-dimensional Reynolds stress model with the data generated from the three-dimensional numerical simulations of upward overshooting in turbulent compressible convection. It has been…

Solar and Stellar Astrophysics · Physics 2020-06-17 Tao Cai

We investigate the influence of the thermal properties of the boundaries in turbulent Rayleigh-Benard convection on analytical bounds on convective heat transport. Using the Doering-Constantin background flow method, we systematically…

Fluid Dynamics · Physics 2008-11-20 Ralf W. Wittenberg

New bounds are proven on the mean vertical convective heat transport, $\overline{\langle wT \rangle}$, for uniform internally heated (IH) convection in the limit of infinite Prandtl number. For fluid in a horizontally-periodic layer between…

Fluid Dynamics · Physics 2023-03-22 Ali Arslan , Giovanni Fantuzzi , John Craske , Andrew Wynn

The effect of helicity (velocity-vorticity correlations) is studied in direct numerical simulations of rotating turbulence down to Rossby numbers of 0.02. The results suggest that the presence of net helicity plays an important role in the…

Fluid Dynamics · Physics 2009-11-13 P. D. Mininni , A. Pouquet

Convection is the predominant mechanism by which energy and angular momentum are transported in the outer portion of the Sun. The resulting overturning motions are also the primary energy source for the solar magnetic field. An accurate…

Solar and Stellar Astrophysics · Physics 2018-03-26 Ryan J. Orvedahl , Michael A. Calkins , Nicholas A. Featherstone , Bradley W. Hindman

Compositional convection is thought to be an important energy source for magnetic field generation within planetary interiors. The Prandtl number, $Pr$, characterizing compositional convection is significantly larger than unity, suggesting…

Geophysics · Physics 2017-04-05 Michael A. Calkins , Keith Julien , Steven M. Tobias

This work investigates heat transport in rotating internally heated convection, for a horizontally periodic fluid between parallel plates under no-slip and isothermal boundary conditions. The main results are the proof of bounds on the mean…

Fluid Dynamics · Physics 2024-12-25 Ali Arslan

In the present work, we explore the Rossby mode instabilities in neutron stars as sources of gravitational waves. The intensity and time evolution of the emitted gravitational waves in terms of the amplitude of the strain tensor are…

We investigate the influence of the thermal properties of the boundaries in turbulent Rayleigh-B\'enard convection on analytical upper bounds on convective heat transport. We model imperfectly conducting bounding plates in two ways: using…

Fluid Dynamics · Physics 2010-08-17 Ralf W. Wittenberg