  Dynamics of flames stabilized downstream of different shape bluff-bodies
(cylindrical, square, star) with different wall topologies (flat, wavy) is
investigated using large-eddy simulations (LES). A two-stage computational
procedure involving the ANSYS software and an in-house academic high-order code
is combined to model a flow in the vicinity of the bluff-bodies and a flame
formed downstream. The fuel is nitrogen-diluted hydrogen and the oxidizer is
hot air in which the fuel auto-ignites. After the ignition, the flame
propagates towards the bluff-body surfaces and stabilizes in their vicinity. It
is shown that the flames reflect the bluff-body shape due to large-scale strong
vortices induced in the shear layer formed between the main recirculation zone
and the oxidizer stream. The influence of the acute corners of the bluff-bodies
on the flame dynamics is quantified by analysing instantaneous and
time-averaged results. Compared to the classical conical bluff-body the largest
differences in the temperature and velocity distributions are observed in the
configuration with the square bluff-body. The main recirculation zone is
shortened by approximately 15% and at its end temperature in the axis of the
flame is almost 200 K larger. Simultaneously, their fluctuations are slightly
larger than in the remaining cases. The influence of the wall topology (flat
vs. wavy) in the configuration with the classical conical bluff-body turned out
to be very small and it resulted in modifications of the flow and flame
structures only in the direct vicinity of the bluff-body surface.
