Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Data-Driven Fractional Subgrid-scale Modeling for Scalar Turbulence: A
  Nonlocal LES Approach   Filtering the passive scalar transport equation in the large-eddy simulation
(LES) of turbulent transport gives rise to the closure term corresponding to
the unresolved scalar flux. Understanding and respecting the statistical
features of subgrid-scale (SGS) flux is a crucial point in robustness and
predictability of the LES. In this work, we investigate the intrinsic nonlocal
behavior of the SGS passive scalar flux through studying its two-point
statistics obtained from the filtered direct numerical simulation (DNS) data
for passive scalar transport in homogeneous isotropic turbulence (HIT).
Presence of long-range correlations in true SGS scalar flux urges to go beyond
the conventional local closure modeling approaches that fail to predict the
non-Gaussian statistical features of turbulent transport in passive scalars.
Here, we propose an appropriate statistical model for microscopic SGS motions
by taking into account the filtered Boltzmann transport equation (FBTE) for
passive scalar. In FBTE, we approximate the filtered equilibrium distribution
with an $\alpha$-stable Levy distribution that essentially incorporates a
power-law behavior to resemble the observed nonlocal statistics of SGS scalar
flux. Generic ensemble-averaging of such FBTE lets us formulate a continuum
level closure model for the SGS scalar flux appearing in terms of
fractional-order Laplacian that is inherently nonlocal. Through a data-driven
approach, we infer the optimal version of our SGS model using the high-fidelity
data for the two-point correlation function between the SGS scalar flux and
filtered scalar gradient, and sparse linear regression. In an \textit{a priori}
test, the optimal fractional-order model yields a promising performance in
reproducing the probability distribution function (PDF) of the SGS dissipation
of the filtered scalar variance compared to its true PDF obtained from the
filtered DNS data.

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The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
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The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
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The categories of this paper are: nlin
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: chem-ph
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The categories of this paper are: q-fin
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The categories of this paper are: stat