Simulations of combustion roar in turbulent attached and lifted turbulent methane jet flames

The present work presents sample results of preliminary computations of the turbulent
aerothermodynamic flow field and of the noise generated by the flame front, due to turbulent
fluctuations in the flame (combustion roar), in lifted and attached jet diffusion flames
of methane. The two-dimensional (2D) time-dependent numerical model was built based on
Reynolds-averaged Navier–Stokes (N-S) equations, equipped with the standard k-e turbulence
models to calculate the reacting jet flows. A reactedness – mixture fraction two-scalar exponential
PDF model, based on non-premixed flame arguments, was combined with a local
Damkohler number extinction criterion to delineate between the reacting and non-reacting
regions. Although the inclusion of the effects of premixed flame propagation could help to
improve the model, initial comparisons with experimental results suggest adequate qualitative
agreement between the computations and reported data. The reasonable agreement obtained
for the aerothermodynamic flame characteristics permitted a meaningful computation of the
combustion noise (roar) characteristics of the studied flames, in order to address the coupled
effects of heat release by the flame and turbulent interactions on the autonomous flame noise
generation.