Anisotropy of Reynolds Stresses and Their Dissipation Rates in Lean H 2 -Air Premixed Flames in Different Combustion Regimes

Nilanjan Chakraborty (), Sanjeev Kumar Ghai and Hong G. Im
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Nilanjan Chakraborty: School of Engineering, University of Newcastle, Claremont Road, Newcastle upon Tyne NE1 7RU, UK
Sanjeev Kumar Ghai: School of Engineering, University of Newcastle, Claremont Road, Newcastle upon Tyne NE1 7RU, UK
Hong G. Im: Clean Combustion Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia

Energies, 2024, vol. 17, issue 21, 1-12

Abstract: The interrelation between Reynolds stresses and their dissipation rate tensors for different Karlovitz number values was analysed using a direct numerical simulation (DNS) database of turbulent statistically planar premixed H 2 -air flames with an equivalence ratio of 0.7. It was found that a significant enhancement of Reynolds stresses and dissipation rates takes place as a result of turbulence generation due to thermal expansion for small and moderate Karlovitz number values. However, both Reynolds stresses and dissipation rates decrease monotonically within the flame brush for large Karlovitz number values, as the flame-generated turbulence becomes overridden by the strong isotropic turbulence. Although there are similarities between the anisotropies of Reynolds stress and its dissipation rate tensors within the flame brush, the anisotropy tensors of these quantities are found to be non-linearly related. The predictions of three different models for the dissipation rate tensor were compared to the results computed from DNS data. It was found that the model relying upon isotropy and a linear dependence between the Reynolds stress and its dissipation rates does not correctly capture the turbulence characteristics within the flame brush for small and moderate Karlovitz number values. In contrast, the models that incorporate the dependence of the invariants of the anisotropy tensor of Reynolds stresses were found to capture the components of dissipation rate tensor for all Karlovitz number conditions.

Keywords: Reynolds stress; viscous dissipation rate; anisotropy; turbulent premixed flame; direct numerical simulations (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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