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INTERACTIONS OF TURBULENCE AND SCALARS IN SHEAR-DRIVEN PREMIXED TURBULENT FLAMES USING DNS

Haiou Wang
School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052, Australia

Evatt R. Hawkes
School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052, Australia; School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney, NSW 2052, Australia

Hemanth Kolla
Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551, USA

Jacqueline H. Chen
Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551, USA

Résumé

The DNS database of modelling lean H2/air combustion in a temporally evolving premixed slot-jet configuration is employed to investigate turbulence-scalar interactions in turbulent reacting flows. In contrast to previous DNS studies of turbulent premixed flames, a mean shear exists in the flow and drives the generation of small-scale turbulence in the shear layer. The orientations of the flame normal and vorticity are examined. It is found that the flame normal preferentially aligns with the most compressive strain rate of the mean flow and the vorticity preferentially aligns with the most extensive mean strain rate. The former is consistent with the fact that the flame front has a tendency to align with the extensive strain rate, while the latter is related to vortex stretching in turbulent flows. The alignment characteristics of the flame normal, vorticity, and turbulent strain rate field conditioned on various progress variable iso-surfaces are investigated. Their influence on the scalar gradients and the vorticity production reflecting the turbulence-scalar interactions are examined quantitatively.