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Effects of buoyancy on turbulent scalar flux closure for turbulent premixed flames in the context of Reynolds Averaged Navier–Stokes simulations

Lookup NU author(s): Arun Varma, Dr Umair AhmedORCiD, Professor Nilanjan ChakrabortyORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. The effects of body force on the statistical behaviour of turbulent scalar flux and its closure in the context of Reynolds Averaged Navier–Stokes simulations have been studied using Direct Numerical Simulations (DNS) of statistically planar turbulent premixed flames under different turbulence intensities and Froude numbers. An increase in body force magnitude in the case of unstable density stratification has been found to augment flame wrinkling, burning rate and gradient transport in comparison to a case without body force but with statistically similar unburned gas turbulence. By contrast, an increase in body force magnitude in the case of stable stratification reduces the flame wrinkling, burning rate and gradient transport in comparison to the flame without body force subjected to statistically similar unburned gas turbulence. Based on a-priori DNS analysis, an algebraic closure for turbulent scalar flux has been identified where the Froude number effects are explicitly accounted for. The body force has been found to have significant influence on the statistical behaviours and magnitudes of the terms of the scalar flux transport equation and this effect is particularly strong for the mean pressure gradient term in the scalar flux transport equation. Based on a detailed a priori DNS analysis, suitable model expressions have been identified for the turbulent transport, pressure gradient, dissipation and reaction rate-velocity correlation terms of the scalar flux transport equation by incorporating the effects of body force (e.g. Froude number effects) for improved model performance.

Publication metadata

Author(s): Varma AR, Ahmed U, Chakraborty N

Publication type: Article

Publication status: Published

Journal: Combustion Theory and Modelling

Year: 2022

Volume: 26

Issue: 4

Pages: 686-711

Online publication date: 19/03/2022

Acceptance date: 28/02/2022

Date deposited: 28/02/2022

ISSN (print): 1364-7830

ISSN (electronic): 1741-3559

Publisher: Taylor and Francis Ltd

URL: https://doi.org/10.1080/13647830.2022.2049881

DOI: 10.1080/13647830.2022.2049881

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