scholarly journals Flow topology dynamics in a three-dimensional phase space for turbulent Rayleigh-Bénard convection

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
F. Dabbagh ◽  
F. X. Trias ◽  
A. Gorobets ◽  
A. Oliva
Keyword(s):  
Phase Space ◽  
Three Dimensional ◽  
Flow Topology ◽  
Bénard Convection ◽  
Dimensional Phase Space ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Exploring the severely confined regime in Rayleigh–Bénard convection

2016 ◽  
Vol 805 ◽  
Author(s):  
Kai Leong Chong ◽  
Ke-Qing Xia
Keyword(s):  
Rayleigh Number ◽  
Flow Topology ◽  
Thermal Plumes ◽  
Bénard Convection ◽  
Benard Convection ◽  
Wide Range ◽  
Classical Boundary ◽  
Global And Local ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

We study the effect of severe geometrical confinement in Rayleigh–Bénard convection with a wide range of width-to-height aspect ratio $\unicode[STIX]{x1D6E4}$, $1/128\leqslant \unicode[STIX]{x1D6E4}\leqslant 1$, and Rayleigh number $Ra$, $3\times 10^{4}\leqslant Ra\leqslant 1\times 10^{11}$, at a fixed Prandtl number of $Pr=4.38$ by means of direct numerical simulations in Cartesian geometry with no-slip walls. For convection under geometrical confinement (decreasing $\unicode[STIX]{x1D6E4}$ from 1), three regimes can be recognized (Chong et al., Phys. Rev. Lett., vol. 115, 2015, 264503) based on the global and local properties in terms of heat transport, plume morphology and flow structures. These are Regime I: classical boundary-layer-controlled regime; Regime II: plume-controlled regime; and Regime III: severely confined regime. The study reveals that the transition into Regime III leads to totally different heat and momentum transport scalings and flow topology from the classical regime. The convective heat transfer scaling, in terms of the Nusselt number $Nu$, exhibits the scaling $Nu-1\sim Ra^{0.61}$ over three decades of $Ra$ at $\unicode[STIX]{x1D6E4}=1/128$, which contrasts sharply with the classical scaling $Nu-1\sim Ra^{0.31}$ found at $\unicode[STIX]{x1D6E4}=1$. The flow in Regime III is found to be dominated by finger-like, long-lived plume columns, again in sharp contrast with the mushroom-like, fragmented thermal plumes typically observed in the classical regime. Moreover, we identify a Rayleigh number for regime transition, $Ra^{\ast }=(29.37/\unicode[STIX]{x1D6E4})^{3.23}$, such that the scaling transition in $Nu$ and $Re$ can be clearly demonstrated when plotted against $Ra/Ra^{\ast }$.

scholarly journals Buoyancy statistics in moist turbulent Rayleigh–Bénard convection

2010 ◽  
Vol 648 ◽  
pp. 509-519 ◽  
Author(s):  
JÖRG SCHUMACHER ◽  
OLIVIER PAULUIS
Keyword(s):  
Piecewise Linear ◽  
Three Dimensional ◽  
Boussinesq Approximation ◽  
Phase Changes ◽  
Bénard Convection ◽  
Benard Convection ◽  
Convection Layer ◽  
The Impact ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

We study shallow moist Rayleigh–Bénard convection in the Boussinesq approximation in three-dimensional direct numerical simulations. The thermodynamics of phase changes is approximated by a piecewise linear equation of state close to the phase boundary. The impact of phase changes on the turbulent fluctuations and the transfer of buoyancy through the layer is discussed as a function of the Rayleigh number and the ability to form liquid water. The enhanced buoyancy flux due to phase changes is compared with dry convection reference cases and related to the cloud cover in the convection layer. This study indicates that the moist Rayleigh–Bénard problem offers a practical framework for the development and evaluation of parameterizations for atmospheric convection.

scholarly journals On the evolution of flow topology in turbulent Rayleigh-Bénard convection

2016 ◽  
Vol 28 (11) ◽  
pp. 115105 ◽  
Author(s):  
F. Dabbagh ◽  
F. X. Trias ◽  
A. Gorobets ◽  
A. Oliva
Keyword(s):  
Flow Topology ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

scholarly journals Three-dimensional visualization of columnar vortices in rotating Rayleigh–Bénard convection

2020 ◽  
Vol 23 (4) ◽  
pp. 635-647
Author(s):  
Kodai Fujita ◽  
Yuji Tasaka ◽  
Takatoshi Yanagisawa ◽  
Daisuke Noto ◽  
Yuichi Murai
Keyword(s):  
Three Dimensional ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Turbulent Rayleigh–Bénard convection in a near-critical fluid by three-dimensional direct numerical simulation

2009 ◽  
Vol 619 ◽  
pp. 127-145 ◽  
Author(s):  
G. ACCARY ◽  
P. BONTOUX ◽  
B. ZAPPOLI
Keyword(s):  
Numerical Simulations ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Thermal Balance ◽  
Transition To Turbulence ◽  
Convective Structures ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

This paper presents state of the art three-dimensional numerical simulations of the Rayleigh–Bénard convection in a supercritical fluid. We consider a fluid slightly above its critical point in a cube-shaped cell heated from below with insulated sidewalls; the thermodynamic equilibrium of the fluid is described by the van der Waals equation of state. The acoustic filtering of the Navier–Stokes equations is revisited to account for the strong stratification of the fluid induced by its high compressibility under the effect of its own weight. The hydrodynamic stability of the fluid is briefly reviewed and we then focus on the convective regime and the transition to turbulence. Direct numerical simulations are carried out using a finite volume method for Rayleigh numbers varying from 106 up to 108. A spatiotemporal description of the flow is presented from the convection onset until the attainment of a statistically steady state of heat transfer. This description concerns mainly the identification of the vortical structures in the flow, the distribution of the Nusselt numbers on the horizontal isothermal walls, the structure of the temperature field and the global thermal balance of the cavity. We focus on the influence of the strong stratification of the fluid on the penetrability of the convective structures in the core of the cavity and on its global thermal balance. Finally, a comparison with the case of a perfect gas, at the same Rayleigh number, is presented.

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