Effect of von Kármán vortex shedding on regular and open-slit V-gutter stabilized turbulent premixed flames

The commercial code FLUENT is used for modeling and simulation of threeand twodimensional non-reacting and reacting flows past regular and open-slit V-gutters. Incompressible Large-Eddy Simulations with Dynamic Subgrid Kinetic Energy Model, C-progress variable equation and Zimont turbulent flame speed closure are used. C3H8 is used as the fuel. The measured and predicted time-averaged streamwise velocity and r.m.s velocity are qualitatively similar for both threeand two-dimensional regular V-gutters under non-reacting conditions. However, the two-dimensional geometry predicts a longer recirculation zone, but shifted upstream. The two-dimensional geometry overpredicts the turbulence fluctuation downstream the flameholder, whereas the three-dimensional geometry underpredicts it. The two-dimensional geometry exhibits greater drag coefficient (CD) per unit flameholder width than that of the corresponding three-dimensional geometry. However, the Strouhal numbers (St) for both geometries are similar. In contrast to the two-dimensional regular V-gutter, the two-dimensional open-slit V-gutter contains no recirculation zone, it is likely dominated by shear layer instability, and exhibits a reduced drag coefficient (CD) (i.e., 29% reduction). The two-dimensional, stoichiometric turbulent premixed flame anchored to the tip of the regular V-gutter exhibits a shear layer immediately downstream the flameholder, and further downstream vortex shedding is pronounced. On the other hand, the flame attached to the open-slit V-gutter does not shed large vortices. This flame is attached to the flameholder boundary layers as well as on the flameholder leading edges. It also contains a jet-like reaction zone due to the slit. The stoichiometric flame attached to the open-slit V-gutter appears to be dynamically stable compared to that attached to the regular V-gutter flameholder. With drastic reductions in equivalence ratio ( the flame structures change dramatically in both flameholders. Both flame lengths shrink and large scale disruptions occur downstream with vortex shedding carrying reaction zones. Flames in both flameholders do not attach when  Finally, based on product formation rate (SC) and vorticity (3) contours, spectral analysis, and standard Rayleigh index, a trade-off between static and dynamic stability is evident.