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Analysis of sub-grid modelling for LES of supercritical flows

Analysis of sub-grid modelling for LES of supercritical flows
Analysis of sub-grid modelling for LES of supercritical flows
The thermodynamic and transport properties of fluids above their critical pressure deviate significantly from those of an ideal gas. This numerical study addresses the effect of real gas properties on the behaviour and Large Eddy Simulation (LES) modelling of supercritical flow. The focus is on thermal mixing in nitrogen, above the critical pressure, but spanning the pseudo-boiling temperature; modelling of these conditions is challenging because they exhibit steep gradients of density and other physical properties. Applying a volume-corrected Peng-Robinson real-gas equation of state and real gas transport models, three supercritical flow configurations have been considered. The simplest involves a thermally inhomogeneous constant pressure system; the second, thermal mixing in a laminar counterflow; and third, a LES of a turbulent jet of cold nitrogen mixing with a hot environment. The analysis leads to two novel conclusions for transcritical flows. First, it has been shown that at low temperatures close to the pseudoboiling temperature, the LES filtered density depends strongly on sub-filter temperature variance, and consequently that thermal dissipation leads to a source term for filtered density. Second, that sub-filter temperature stratification causes anisotropy in the effective molecular viscosity – reducing the effective viscosity for shear normal to the temperature gradient, and similarly reducing the effective thermal conductivity below its mean value. It is found, however, that the LES methodology presented here predicts the mean density profile of the turbulent nitrogen jet adequately, even though the LES modelling neglects sub-grid property fluctuations.
SFB TRR40
Richardson, E.S.
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Jarczyk, M.
7cf4c748-dfc6-4b0d-ae1c-489dc52aadba
Pohl, S.
d3383144-5b81-4211-9401-396d739ea719
Pfitzner, M.
ae2f26e8-6c70-488d-b9f9-e4409a713a9a
Richardson, E.S.
a8357516-e871-40d8-8a53-de7847aa2d08
Jarczyk, M.
7cf4c748-dfc6-4b0d-ae1c-489dc52aadba
Pohl, S.
d3383144-5b81-4211-9401-396d739ea719
Pfitzner, M.
ae2f26e8-6c70-488d-b9f9-e4409a713a9a

Richardson, E.S., Jarczyk, M., Pohl, S. and Pfitzner, M. (2011) Analysis of sub-grid modelling for LES of supercritical flows. In Proceedings of the SFB TRR40 Summer Program. SFB TRR40. 17 pp .

Record type: Conference or Workshop Item (Paper)

Abstract

The thermodynamic and transport properties of fluids above their critical pressure deviate significantly from those of an ideal gas. This numerical study addresses the effect of real gas properties on the behaviour and Large Eddy Simulation (LES) modelling of supercritical flow. The focus is on thermal mixing in nitrogen, above the critical pressure, but spanning the pseudo-boiling temperature; modelling of these conditions is challenging because they exhibit steep gradients of density and other physical properties. Applying a volume-corrected Peng-Robinson real-gas equation of state and real gas transport models, three supercritical flow configurations have been considered. The simplest involves a thermally inhomogeneous constant pressure system; the second, thermal mixing in a laminar counterflow; and third, a LES of a turbulent jet of cold nitrogen mixing with a hot environment. The analysis leads to two novel conclusions for transcritical flows. First, it has been shown that at low temperatures close to the pseudoboiling temperature, the LES filtered density depends strongly on sub-filter temperature variance, and consequently that thermal dissipation leads to a source term for filtered density. Second, that sub-filter temperature stratification causes anisotropy in the effective molecular viscosity – reducing the effective viscosity for shear normal to the temperature gradient, and similarly reducing the effective thermal conductivity below its mean value. It is found, however, that the LES methodology presented here predicts the mean density profile of the turbulent nitrogen jet adequately, even though the LES modelling neglects sub-grid property fluctuations.

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More information

Published date: 2011
Venue - Dates: SFB TRR40 Summer Program, 2011-07-31 - 2011-08-25
Related URLs:
Organisations: Faculty of Engineering and the Environment

Identifiers

Local EPrints ID: 333606
URI: http://eprints.soton.ac.uk/id/eprint/333606
PURE UUID: bdd91c14-cd7b-42e5-b4c1-abf20a82aa93

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Date deposited: 07 Mar 2012 15:28
Last modified: 30 Sep 2020 16:33

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Contributors

Author: E.S. Richardson
Author: M. Jarczyk
Author: S. Pohl
Author: M. Pfitzner

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