Statistics conditioned to isoscalar surfaces in highly turbulent premixed reacting systems
(2019) In Computers and Fluids 187. p.69-82- Abstract
The paper aims at clarifying some issues associated with evaluation of surface-averaged quantities in Direct Numerical Simulation (DNS) of a turbulent reacting flow. For a quantity ϕ(t, x) averaged over an isosurface c(t,x)=c^ of a reaction progress variable c, there exist at least two different definitions of surface averages; an area-weighted surface average 〈ϕ〉
s
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The paper aims at clarifying some issues associated with evaluation of surface-averaged quantities in Direct Numerical Simulation (DNS) of a turbulent reacting flow. For a quantity ϕ(t, x) averaged over an isosurface c(t,x)=c^ of a reaction progress variable c, there exist at least two different definitions of surface averages; an area-weighted surface average 〈ϕ〉
s
|
c^,t
and an unweighted surface average 〈ϕ〉
v
|
c^,t
. These two fine-grained averages can also be extended to coarse-grained surface averages 〈ϕ〉
S
|
c^,ϵ,t
and 〈ϕ〉
V
|
c^,ϵ,t
over an interval of c^≤c(t,x)≤c^+ϵ. In a highly turbulent medium, the difference 〈ϕ〉
s
−〈ϕ〉
v
between the area-weighted and unweighted surface averages can be significant for most quantities ϕ of basic interest. The sign of this difference depends on the sign of the correlation between ϕ and |∇c|, can be opposite for different ϕ or even for different isosurfaces of the same scalar field ϕ. For a quantity ϕ that can become singular in the zero-gradient points |∇c|(t,x)=0, its unweighted or area-weighted surface averages can still be bounded. The difference between area-weighted and unweighted surface averages of 1/|∇c| or |∇c| is relevant to explaining the well-known, but still challenging controversy between available data on the influence of turbulence on the local flame thickness.
- author
- Yu, Rixin LU and Lipatnikov, Andrei N.
- organization
- publishing date
- 2019
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Conditioned statistics, DNS, Turbulent reacting flow
- in
- Computers and Fluids
- volume
- 187
- pages
- 69 - 82
- publisher
- Elsevier
- external identifiers
-
- scopus:85065011526
- ISSN
- 0045-7930
- DOI
- 10.1016/j.compfluid.2019.04.017
- language
- English
- LU publication?
- yes
- id
- b59d86ea-5c18-4e83-8f29-edb5085013a2
- date added to LUP
- 2019-05-17 13:00:31
- date last changed
- 2022-04-25 23:44:18
@article{b59d86ea-5c18-4e83-8f29-edb5085013a2,
abstract = {{<p><br>
The paper aims at clarifying some issues associated with evaluation of surface-averaged quantities in Direct Numerical Simulation (DNS) of a turbulent reacting flow. For a quantity ϕ(t, x) averaged over an isosurface c(t,x)=c^ of a reaction progress variable c, there exist at least two different definitions of surface averages; an area-weighted surface average 〈ϕ〉 <br>
<sub><br>
<br>
<sub>s</sub><br>
<br>
</sub><br>
| <br>
<sub>c^,t</sub><br>
and an unweighted surface average 〈ϕ〉 <br>
<sub><br>
<br>
<sub>v</sub><br>
<br>
</sub><br>
| <br>
<sub>c^,t</sub><br>
. These two fine-grained averages can also be extended to coarse-grained surface averages 〈ϕ〉 <br>
<sub><br>
<br>
<sub>S</sub><br>
<br>
</sub><br>
| <br>
<sub>c^,ϵ,t</sub><br>
and 〈ϕ〉 <br>
<sub><br>
<br>
<sub>V</sub><br>
<br>
</sub><br>
| <br>
<sub>c^,ϵ,t</sub><br>
over an interval of c^≤c(t,x)≤c^+ϵ. In a highly turbulent medium, the difference 〈ϕ〉 <br>
<sub><br>
<br>
<sub>s</sub><br>
<br>
</sub><br>
−〈ϕ〉 <br>
<sub><br>
<br>
<sub>v</sub><br>
<br>
</sub><br>
between the area-weighted and unweighted surface averages can be significant for most quantities ϕ of basic interest. The sign of this difference depends on the sign of the correlation between ϕ and |∇c|, can be opposite for different ϕ or even for different isosurfaces of the same scalar field ϕ. For a quantity ϕ that can become singular in the zero-gradient points |∇c|(t,x)=0, its unweighted or area-weighted surface averages can still be bounded. The difference between area-weighted and unweighted surface averages of 1/|∇c| or |∇c| is relevant to explaining the well-known, but still challenging controversy between available data on the influence of turbulence on the local flame thickness. <br>
</p>}},
author = {{Yu, Rixin and Lipatnikov, Andrei N.}},
issn = {{0045-7930}},
keywords = {{Conditioned statistics; DNS; Turbulent reacting flow}},
language = {{eng}},
pages = {{69--82}},
publisher = {{Elsevier}},
series = {{Computers and Fluids}},
title = {{Statistics conditioned to isoscalar surfaces in highly turbulent premixed reacting systems}},
url = {{http://dx.doi.org/10.1016/j.compfluid.2019.04.017}},
doi = {{10.1016/j.compfluid.2019.04.017}},
volume = {{187}},
year = {{2019}},
}