Solenoidal and potential velocity fields in weakly turbulent premixed flames

Abstract Direct Numerical Simulation data obtained earlier from two statistically 1D, planar, fully-developed, weakly turbulent, single-step-chemistry, premixed flames characterized by different (7.53 and 2.50) density ratios ? are analyzed to explore the influence of combustion-induced thermal expansion on turbulence backward such flow perturbations reaction zone. For this purpose, actual velocity fields decomposed into solenoidal potential subfields, followed independently processing each subfield. Results show that velocities negatively (positively) correlated in unburned reactants (burned products, respectively) provided = 7.53 . Moreover, not only potential, but also subfields contribute countergradient turbulent scalar transport. Furthermore, correlation between strain rates generated conditioned zone is positive (negative) leading (trailing, halves mean flame brushes. The rate correlates with curvature within zone, whereas If , stretch negative (positive) regions large (negative, rates, opposite trend observed for rate. Thus, differently affect In case 2.5 differences significantly less pronounced. Finally, an approximate decomposition viscous dissipation kinetic energy contributions suggested supported DNS data. results dilatation-induced plays important role. Therefore, reduced increase mixture viscosity rotational