A Numerical Study of Upper Bounds on the Heat Transport by Turbulent Convection in a Fluid Layer Heated from Below

1996 ◽  
pp. 283-284
Author(s):  
N. K. Vitanov ◽  
F. H. Busse
Keyword(s):  
Heat Transport ◽  
Numerical Study ◽  
Fluid Layer ◽  
Upper Bounds ◽  
Turbulent Convection

Enhanced heat transport in partitioned thermal convection

2015 ◽  
Vol 784 ◽  
Author(s):  
Yun Bao ◽  
Jun Chen ◽  
Bo-Fang Liu ◽  
Zhen-Su She ◽  
Jun Zhang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Numerical Study ◽  
Fluid Layer ◽  
Convection Cell ◽  
Heat Transfer Efficiency ◽  
Self Organized ◽  
Partition Walls ◽  
Open Question ◽  
Rayleigh Benard

Enhancement of heat transport across a fluid layer is of fundamental interest as well as great technological importance. For decades, Rayleigh–Bénard convection has been a paradigm for the study of convective heat transport, and how to improve its overall heat-transfer efficiency is still an open question. Here, we report an experimental and numerical study that reveals a novel mechanism that leads to much enhanced heat transport. When vertical partitions are inserted into a convection cell with thin gaps left open between the partition walls and the cooling/heating plates, it is found that the convective flow becomes self-organized and more coherent, leading to an unprecedented heat-transport enhancement. In particular, our experiments show that with six partition walls inserted, the heat flux can be increased by approximately 30 %. Numerical simulations show a remarkable heat-flux enhancement of up to 2.3 times (with 28 partition walls) that without any partitions.

scholarly journals Steady Rayleigh–Bénard convection between no-slip boundaries

2021 ◽  
Vol 933 ◽  
Author(s):  
Baole Wen ◽  
David Goluskin ◽  
Charles R. Doering
Keyword(s):  
Heat Transport ◽  
Fluid Layer ◽  
Turbulent Convection ◽  
Bénard Convection ◽  
Benard Convection ◽  
Convection Rolls ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Steady Convection ◽  
Asymptotic Scaling

The central open question about Rayleigh–Bénard convection – buoyancy-driven flow in a fluid layer heated from below and cooled from above – is how vertical heat flux depends on the imposed temperature gradient in the strongly nonlinear regime where the flows are typically turbulent. The quantitative challenge is to determine how the Nusselt number $Nu$ depends on the Rayleigh number $Ra$ in the $Ra\to \infty$ limit for fluids of fixed finite Prandtl number $Pr$ in fixed spatial domains. Laboratory experiments, numerical simulations and analysis of Rayleigh's mathematical model have yet to rule out either of the proposed ‘classical’ $Nu \sim Ra^{1/3}$ or ‘ultimate’ $Nu \sim Ra^{1/2}$ asymptotic scaling theories. Among the many solutions of the equations of motion at high $Ra$ are steady convection rolls that are dynamically unstable but share features of the turbulent attractor. We have computed these steady solutions for $Ra$ up to $10^{14}$ with $Pr=1$ and various horizontal periods. By choosing the horizontal period of these rolls at each $Ra$ to maximize $Nu$ , we find that steady convection rolls achieve classical asymptotic scaling. Moreover, they transport more heat than turbulent convection in experiments or simulations at comparable parameters. If heat transport in turbulent convection continues to be dominated by heat transport in steady rolls as $Ra\to \infty$ , it cannot achieve the ultimate scaling.

scholarly journals Stellar Convection as a Low Prandtl Number Flow

1991 ◽  
Vol 130 ◽  
pp. 57-61
Author(s):  
Josep M. Massaguer
Keyword(s):  
Nusselt Number ◽  
Prandtl Number ◽  
Heat Transport ◽  
Large Scale ◽  
Shear Layers ◽  
Turbulent Convection ◽  
The Sun ◽  
Stellar Convection ◽  
Cool Stars ◽  
Number Flow

AbstractThermal convection in the Sun and cool stars is often modeled with the assumption of an effective Prandtl number σ ≃ 1. Such a parameterization results in masking of the presence of internal shear layers which, for small σ, might control the large scale dynamics. In this paper we discuss the relevance of such layers in turbulent convection. Implications for heat transport – i.e. for the Nusselt number power law – are also discussed.

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