Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: What rotation rate maximizes heat transport in rotating
  Rayleigh-B\'{e}nard convection with Prandtl number larger than one?   The heat transfer and flow structure in rotating Rayleigh-B\'enard convection
are strongly influenced by the Rayleigh ($Ra$), Prandtl ($Pr$), and Rossby
($Ro$) number. For $Pr\gtrsim 1$ and intermediate rotation rates, the heat
transfer is increased compared to the non-rotating case. We find that the
regime of increased heat transfer is subdivided into a low and a high $Ra$
number regime. For $Ra\lesssim 5\times10^8$ the heat transfer at a given $Ra$
and $Pr$ is highest at an optimal rotation rate, at which the thickness of the
viscous and thermal boundary layer is about equal. From the scaling relations
of the thermal and viscous boundary layer thicknesses, we derive that the
optimal rotation rate scales as $1/Ro_\mathrm{opt} \approx 0.12
Pr^{1/2}Ra^{1/6}$. In the low $Ra$ regime the heat transfer is similar in a
periodic domain and cylindrical cells with different aspect ratios, i.e.\ the
ratio of diameter to height. This is consistent with the view that the
vertically aligned vortices are the dominant flow structure. For $Ra\gtrsim
5\times10^8$ the above scaling for the optimal rotation rate does not hold
anymore. It turns out that in the high $Ra$ regime, the flow structures at the
optimal rotation rate are very different than for lower $Ra$. Surprisingly, the
heat transfer in the high $Ra$ regime differs significantly for a periodic
domain and cylindrical cells with different aspect ratios, which originates
from the sidewall boundary layer dynamics and the corresponding secondary
circulation.

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The categories of this paper are: stat
37
The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: math
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: ao-sci