SANDIA Flame D

Application Challenge AC2-09 © copyright ERCOFTAC 2024

Comparison of Test Data and CFD

In this section comparisons of the CFD results and test data are organized as follows:

Comparisons of two different approaches for modeling the turbulence/combustion interaction, namely: steady flamelet model and simplified Conditional Moment Closure (designated as CMC -model in the figures from here on) obtained with the classical Smagorinsky subgrid scale model,

Comparisons of two subgrid-scale models, namely: classical Smagorinsky subgrid scale model and dynamic Smagorinsky one using the steady flamelet model of turbulence/combustion interaction.

Fig.6. shows mean velocity axial component and mixture fraction along the centerline for both steady flamelet and CMC approaches. One can see quite significant discrepancies between both models. Steady flamelet shows rapid velocity decay in the near field and then the slope is quite close to the one measured experimentally. On the other hand the CMC model leads to much smaller velocity decay. The velocity profile for CMC is closer to experimental data but the slope at the distance z/D=10 is underpredicted. At the distance z/D=30 both models predict good velocity decay. As to the mixture fraction both models predict quite a long distance z/D ≤ 16 for which the mixture fraction is unity while the experiment showed much more intense mixing in this region. As a consequence, at the jet centerline for a distance z/D ≤ 16 the numerical models do not predict reaction and this is reflected in the temperature profile and combustion products like CO₂ shown in Fig.8. However, further downstream in the fully developed flame the numerical results are much closer to the experimental data. Especially CMC predicts the value of temperature maximum and its location with quite high accuracy (see Fig.7).