Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effective Medium Theory for Drag Reducing Micro-patterned Surfaces in
  Turbulent Flows   Inspired by the lotus effect, many studies in the last decade have focused on
micro- and nano-patterned surfaces. They revealed that patterns at the
micro-scale combined with high contact angles can significantly reduce skin
drag. However, the mechanisms and parameters that control drag reduction, e.g.
Reynolds number and pattern geometry, are still unclear. We propose an
effective medium representation of the micro-features, that treats the latter
as a porous medium, and provides a framework to model flow over patterned
surfaces in both Cassie and Wenzel states. Our key result is a closed-form
expression for the skin friction coefficient in terms of frictional Reynolds
(or K\'arm\'an) number in turbulent regime, the viscosity ratio between the
fluid in and above the features, and their geometrical properties. We apply the
proposed model to turbulent flows over superhydrophobic ridged surfaces. The
model predictions agree with laboratory experiments for Reynolds numbers
ranging from 3000 to 10000.

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The categories of this paper are: dg-ga
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph